build: Remove unsupported install directives

We're using the `install` argument for configure_file() all over the
place.

The support for an `install` argument for configure_file() was added in
Meson 0.50, but we haven't bumped the minimum version of Meson we
require, yet; which means we're getting compatibility warnings when
using recent versions of Meson, and undefined behaviour when using older
versions.

The configure_file() object defaults to `install: false`, unless an
install directory is used. This means that all instances of an `install`
argument with an explicit `true` or `false` value can be removed,
whereas all instances of `install` with a value determined from a
configuration option must be turned into an explicit conditional.

gio/gdbus-2.0/codegen/meson.build

@@ -16,7 +16,6 @@ gdbus_codegen_conf.set('DATADIR', glib_datadir)
 # Install gdbus-codegen executable
 gdbus_codegen = configure_file(input : 'gdbus-codegen.in',
   output : 'gdbus-codegen',
-  install : true,
   install_dir : get_option('bindir'),
   configuration : gdbus_codegen_conf
 )
@@ -28,7 +27,6 @@ codegen_dir = join_paths(get_option('datadir'), 'glib-2.0/codegen')
 gdbus_codegen_built_files = []
 gdbus_codegen_built_files += configure_file(input : 'config.py.in',
                                             output : 'config.py',
-                                            install : true,
                                             install_dir : codegen_dir,
                                             configuration : gdbus_codegen_conf)
 
@@ -36,7 +34,6 @@ foreach f : gdbus_codegen_files
   # Copy these into the builddir so that gdbus-codegen can be used uninstalled
   # and then install it too so that it can be used after installation
   gdbus_codegen_built_files += configure_file(input : f, output : f,
-                                              install : true,
                                               install_dir : codegen_dir,
                                               copy : true)
 endforeach

gio/meson.build

@@ -996,7 +996,7 @@ if enable_systemtap
     output : '@0@.stp'.format(libgio.full_path().split('/').get(-1)),
     configuration : stp_cdata,
     install_dir : tapset_install_dir,
-    install : true)
+  )
 endif
 
 subdir('fam')

gio/tests/meson.build

@@ -424,13 +424,20 @@ else
 endif
 
 foreach appinfo_test_desktop_file : appinfo_test_desktop_files
-  configure_file(
-    input: appinfo_test_desktop_file + '.in',
-    output: appinfo_test_desktop_file,
-    install_dir: installed_tests_execdir,
-    install: installed_tests_enabled,
-    configuration: cdata,
-  )
+  if installed_tests_enabled
+    configure_file(
+      input: appinfo_test_desktop_file + '.in',
+      output: appinfo_test_desktop_file,
+      install_dir: installed_tests_execdir,
+      configuration: cdata,
+    )
+  else
+    configure_file(
+      input: appinfo_test_desktop_file + '.in',
+      output: appinfo_test_desktop_file,
+      configuration: cdata,
+    )
+  endif
 endforeach
 
 if installed_tests_enabled
@@ -558,7 +565,7 @@ if not meson.is_cross_build() or meson.has_exe_wrapper()
   test_generated_txt = configure_file(input : 'test1.txt',
     output : 'test-generated.txt',
     copy : true,
-    install : false)
+  )
 
   resources_extra_sources = [
     test_gresource,