From: John Zimmermann <johnz@posteo.net>
--- a/cmake/external/crash_reports/CMakeLists.txt
+++ b/cmake/external/crash_reports/CMakeLists.txt
@@ -7,6 +7,7 @@
 add_library(external_crash_reports INTERFACE IMPORTED GLOBAL)
 add_library(desktop-app::external_crash_reports ALIAS external_crash_reports)
 
+if(NOT DESKTOP_APP_DISABLE_CRASH_REPORTS)
 if (WIN32 OR LINUX OR build_macstore)
     add_subdirectory(breakpad)
     target_link_libraries(external_crash_reports
@@ -20,3 +21,4 @@
         desktop-app::external_crashpad
     )
 endif()
+endif()
--- a/cmake/external/ffmpeg/CMakeLists.txt
+++ b/cmake/external/ffmpeg/CMakeLists.txt
@@ -7,6 +7,18 @@
 add_library(external_ffmpeg INTERFACE IMPORTED GLOBAL)
 add_library(desktop-app::external_ffmpeg ALIAS external_ffmpeg)
 
+if(DESKTOP_APP_USE_SYSTEM_LIBS)
+    find_package(PkgConfig REQUIRED)
+    pkg_check_modules(FFMPEG REQUIRED libavcodec libavformat libavutil libswresample libswscale)
+    target_link_libraries(external_ffmpeg
+    INTERFACE
+        ${FFMPEG_LIBRARIES}
+    )
+    target_include_directories(external_ffmpeg SYSTEM
+    INTERFACE
+        ${FFMPEG_INCLUDE_DIRS}
+    )
+else()
 target_include_directories(external_ffmpeg SYSTEM
 INTERFACE
     ${libs_loc}/ffmpeg
@@ -36,3 +48,4 @@
         Xrender
     )
 endif()
+endif()
--- a/cmake/external/openal/CMakeLists.txt
+++ b/cmake/external/openal/CMakeLists.txt
@@ -7,6 +7,21 @@
 add_library(external_openal INTERFACE IMPORTED GLOBAL)
 add_library(desktop-app::external_openal ALIAS external_openal)
 
+if(DESKTOP_APP_USE_SYSTEM_LIBS)
+    find_package(OpenAL REQUIRED)
+    target_include_directories(external_openal SYSTEM
+    INTERFACE
+        ${OPENAL_INCLUDE_DIR}
+    )
+    target_link_libraries(external_openal
+    INTERFACE
+        ${OPENAL_LIBRARY}
+    )
+    target_compile_definitions(external_openal
+    INTERFACE
+        AL_ALEXT_PROTOTYPES
+    )
+else()
 if (WIN32)
     target_include_directories(external_openal SYSTEM
     INTERFACE
@@ -41,3 +56,4 @@
     AL_LIBTYPE_STATIC
     AL_ALEXT_PROTOTYPES
 )
+endif()
--- a/cmake/external/openssl/CMakeLists.txt
+++ b/cmake/external/openssl/CMakeLists.txt
@@ -7,7 +7,13 @@
 add_library(external_openssl INTERFACE IMPORTED GLOBAL)
 add_library(desktop-app::external_openssl ALIAS external_openssl)
 
-if (LINUX)
+if(DESKTOP_APP_USE_SYSTEM_LIBS)
+    find_package(OpenSSL REQUIRED)
+    target_include_directories(external_openssl SYSTEM
+    INTERFACE
+        ${OPENSSL_INCLUDE_DIR}
+    )
+elseif (LINUX)
     target_include_directories(external_openssl SYSTEM
     INTERFACE
         /usr/local/desktop-app/openssl-1.1.1/include
@@ -24,6 +30,13 @@
     )
 endif()
 
+if(DESKTOP_APP_USE_SYSTEM_LIBS)
+    target_link_libraries(external_openssl
+    INTERFACE
+	OpenSSL::Crypto
+        OpenSSL::SSL
+    )
+else()
 if (WIN32)
     set(openssl_lib_ext lib)
     set(openssl_lib_loc ${libs_loc}/openssl_1_1_1/out32$<$<CONFIG:Debug>:.dbg>)
@@ -45,6 +58,7 @@
     ${openssl_lib_loc}/libssl.${openssl_lib_ext}
     ${openssl_lib_loc}/libcrypto.${openssl_lib_ext}
 )
+endif()
 
 if (LINUX)
     if (DESKTOP_APP_USE_GLIBC_WRAPS)
--- a/cmake/external/opus/CMakeLists.txt
+++ b/cmake/external/opus/CMakeLists.txt
@@ -7,6 +7,18 @@
 add_library(external_opus INTERFACE IMPORTED GLOBAL)
 add_library(desktop-app::external_opus ALIAS external_opus)
 
+if(DESKTOP_APP_USE_SYSTEM_LIBS)
+    find_package(PkgConfig REQUIRED)
+    pkg_check_modules(OPUS REQUIRED opus)
+    target_include_directories(external_opus SYSTEM
+    INTERFACE
+        ${OPUS_INCLUDE_DIRS}
+    )
+    target_link_libraries(external_opus
+    INTERFACE
+        ${OPUS_LIBRARIES}
+    )
+else()
 target_include_directories(external_opus SYSTEM
 INTERFACE
     ${libs_loc}/opus/include
@@ -43,3 +55,4 @@
         opus
     )
 endif()
+endif()
--- a/cmake/external/qt/CMakeLists.txt
+++ b/cmake/external/qt/CMakeLists.txt
@@ -15,6 +15,36 @@
     endif()
 endif()
 
+if(DESKTOP_APP_USE_SYSTEM_LIBS)
+    get_target_property(QTCORE_INCLUDE_DIRS Qt5::Core INTERFACE_INCLUDE_DIRECTORIES)
+    list(GET QTCORE_INCLUDE_DIRS 0 QT_INCLUDE_DIR)
+
+    foreach(__qt_module IN ITEMS QtCore QtGui)
+        list(APPEND QT_PRIVATE_INCLUDE_DIRS
+                ${QT_INCLUDE_DIR}/${__qt_module}/${Qt5_VERSION}
+                ${QT_INCLUDE_DIR}/${__qt_module}/${Qt5_VERSION}/${__qt_module}
+        )
+    endforeach()
+    message(STATUS "Using Qt private include directories: ${QT_PRIVATE_INCLUDE_DIRS}")
+    target_include_directories(external_qt SYSTEM
+    INTERFACE
+        ${QT_PRIVATE_INCLUDE_DIRS}
+    )
+    target_link_libraries(external_qt
+    INTERFACE
+        Qt5::DBus
+        Qt5::Network
+        Qt5::Widgets
+        desktop-app::external_zlib
+        xcb
+        X11
+        X11-xcb
+        dbus-1
+        dl
+        glib-2.0
+        pthread
+    )
+else()
 target_include_directories(external_qt SYSTEM
 INTERFACE
     ${qt_loc}/include
@@ -215,3 +245,4 @@
         pthread
     )
 endif()
+endif()
--- a/cmake/external/qt/package.cmake
+++ b/cmake/external/qt/package.cmake
@@ -4,6 +4,9 @@
 # For license and copyright information please follow this link:
 # https://github.com/desktop-app/legal/blob/master/LEGAL
 
+if(DESKTOP_APP_USE_SYSTEM_LIBS)
+
+else()
 if (NOT APPLE OR NOT build_osx)
     set(qt_version 5.12.5)
 else()
@@ -17,6 +20,7 @@
 endif()
 
 set(Qt5_DIR ${qt_loc}/lib/cmake/Qt5)
+endif()
 
 find_package(Qt5 COMPONENTS Core Gui Widgets Network REQUIRED)
 
--- a/cmake/external/zlib/CMakeLists.txt
+++ b/cmake/external/zlib/CMakeLists.txt
@@ -7,6 +7,18 @@
 add_library(external_zlib INTERFACE IMPORTED GLOBAL)
 add_library(desktop-app::external_zlib ALIAS external_zlib)
 
+if(DESKTOP_APP_USE_SYSTEM_LIBS)
+    find_package(ZLIB REQUIRED)
+    find_package(PkgConfig REQUIRED)
+    pkg_check_modules(MINIZIP REQUIRED minizip)
+    find_library(minizip_LIBRARY minizip)
+    target_link_libraries(external_zlib INTERFACE ZLIB::ZLIB ${minizip_LIBRARY})
+    target_include_directories(external_zlib SYSTEM
+    INTERFACE
+	${ZLIB_INCLUDE_DIR}
+        ${MINIZIP_INCLUDE_DIRS}
+    )
+else()
 if (NOT WIN32)
     add_library(external_minizip STATIC)
     init_target(external_minizip "(external)")
@@ -49,3 +61,4 @@
 else()
     target_link_static_libraries(external_zlib INTERFACE z)
 endif()
+endif()
--- a/cmake/init_target.cmake
+++ b/cmake/init_target.cmake
@@ -27,7 +27,7 @@
     endif()
     target_link_libraries(${target_name} PUBLIC desktop-app::common_options)
     set_target_properties(${target_name} PROPERTIES
-        LINK_SEARCH_START_STATIC 1
+        LINK_SEARCH_START_STATIC 0
         XCODE_ATTRIBUTE_CLANG_ENABLE_OBJC_WEAK YES
         XCODE_ATTRIBUTE_GCC_INLINES_ARE_PRIVATE_EXTERN YES
         XCODE_ATTRIBUTE_GCC_SYMBOLS_PRIVATE_EXTERN YES
--- a/cmake/options_linux.cmake
+++ b/cmake/options_linux.cmake
@@ -25,6 +25,9 @@
     -Wno-stringop-overflow
     -Wno-maybe-uninitialized
     -Wno-error=class-memaccess
+    -Wno-error=deprecated-copy
+    -Wno-error=deprecated-declarations
+    -Wno-error=redundant-move
 )
 target_link_options(common_options
 INTERFACE
@@ -33,8 +36,5 @@
 if (build_linux32)
     target_compile_options(common_options INTERFACE -g0)
     target_link_options(common_options INTERFACE -g0)
-else()
-    target_compile_options(common_options INTERFACE $<IF:$<CONFIG:Debug>,,-g -flto>)
-    target_link_options(common_options INTERFACE $<IF:$<CONFIG:Debug>,,-g -flto -fuse-linker-plugin>)
 endif()
 
--- a/cmake/variables.cmake
+++ b/cmake/variables.cmake
@@ -10,6 +10,7 @@
 option(DESKTOP_APP_LOTTIE_USE_CACHE "Use caching in lottie animations." ON)
 option(DESKTOP_APP_USE_GLIBC_WRAPS "Use wraps for new GLIBC features." OFF)
 option(DESKTOP_APP_USE_PACKAGED "Find libraries using CMake instead of exact paths." ON)
+option(DESKTOP_APP_USE_SYSTEM_LIBS "Use system libs where possible." OFF)
 
 function(report_bad_special_target)
     message(FATAL_ERROR "Bad special target '${DESKTOP_APP_SPECIAL_TARGET}'")
@@ -59,8 +60,7 @@
     set(DESKTOP_APP_USE_GLIBC_WRAPS OFF)
 else()
     set(LINUX 1)
-    execute_process(COMMAND uname -m OUTPUT_VARIABLE machine_uname)
-    if (NOT ${machine_uname} MATCHES "x86_64" AND NOT ${machine_uname} MATCHES "aarch64")
+    if (CMAKE_SIZEOF_VOID_P EQUAL 4)
         set(build_linux32 1)
     endif()
     if (DESKTOP_APP_SPECIAL_TARGET STREQUAL "linux")
--- a/cmake/external/lz4/CMakeLists.txt
+++ b/cmake/external/lz4/CMakeLists.txt
@@ -4,8 +4,18 @@
 # For license and copyright information please follow this link:
 # https://github.com/desktop-app/legal/blob/master/LEGAL
 
+if(DESKTOP_APP_USE_SYSTEM_LIBS)
+    add_library(external_lz4 INTERFACE IMPORTED GLOBAL)
+    add_library(desktop-app::external_lz4 ALIAS external_lz4)
+
+    find_package(PkgConfig REQUIRED)
+    pkg_check_modules(LZ4 REQUIRED liblz4)
+    target_link_libraries(external_lz4 INTERFACE ${LZ4_LIBRARIES})
+    target_include_directories(external_lz4 SYSTEM INTERFACE ${LZ4_INCLUDE_DIRS})
+else()
 add_library(external_lz4 OBJECT)
 add_library(desktop-app::external_lz4 ALIAS external_lz4)
+
 init_target(external_lz4 "(external)")
 
 set(lz4_loc ${third_party_loc}/lz4/lib)
@@ -27,3 +37,4 @@
 PUBLIC
     ${lz4_loc}
 )
+endif()
--- a/cmake/external/xxhash/CMakeLists.txt
+++ b/cmake/external/xxhash/CMakeLists.txt
@@ -7,6 +7,10 @@
 add_library(external_xxhash INTERFACE IMPORTED GLOBAL)
 add_library(desktop-app::external_xxhash ALIAS external_xxhash)
 
+if(DESKTOP_APP_USE_SYSTEM_LIBS)
+    find_library(xxhash_LIBRARIES xxhash)
+    target_link_libraries(external_xxhash INTERFACE ${xxhash_LIBRARIES})
+else()
 target_include_directories(external_xxhash SYSTEM
 INTERFACE
     ${third_party_loc}/xxHash
@@ -16,3 +20,4 @@
 INTERFACE
     XXH_INLINE_ALL
 )
+endif()