build: Disable -Wvariadic-macros

We explicitly require support for variadic macros; see
https://wiki.gnome.org/Projects/GLib/CompilerRequirements.

Signed-off-by: Philip Withnall <pwithnall@endlessos.org>

meson.build

@@ -442,6 +442,8 @@ if cc.get_id() == 'gcc' or cc.get_id() == 'clang'
     '-Wno-pedantic',
     # A zero-length format string shouldn't be considered an issue.
     '-Wno-format-zero-length',
+    # We explicitly require variadic macros
+    '-Wno-variadic-macros',
     '-Werror=declaration-after-statement',
     '-Werror=format=2',
     '-Werror=implicit-function-declaration',