build: Always pass --quiet to g-ir-scanner

This makes the build less verbose, as all .gir generation except for
clutters didn't pass --quiet to g-ir-scanner, making it output long
linking commands. Do this by adding a common introspection_args
variable.

While at it, put -U_GNU_SOURCE in there too, as it was always passed
everywhere as without it the scanner would log warnings.

clutter/clutter/meson.build

@@ -540,10 +540,7 @@ libmutter_clutter_dep = declare_dependency(
 )
 
 if have_introspection
-  clutter_introspection_args = clutter_c_args + [
-    '-U_GNU_SOURCE', # _GNU_SOURCE triggers warnings in g-ir-scanner
-    '--quiet',
-  ]
+  clutter_introspection_args = introspection_args + clutter_c_args
 
   libmutter_clutter_gir = gnome.generate_gir(libmutter_clutter,
     sources: [

cogl/cogl-pango/meson.build

@@ -54,10 +54,9 @@ if have_introspection
       pango_dep,
       libmutter_cogl_pango_dep,
     ],
-    extra_args: [
+    extra_args: introspection_args + [
       '-UCOGL_COMPILATION',
       '-DG_LOG_DOMAIN=\"CoglPango\"',
-      '-U_GNU_SOURCE',
     ],
     install_dir_gir: pkglibdir,
     install_dir_typelib: pkglibdir,

cogl/cogl/meson.build

@@ -488,14 +488,13 @@ if have_introspection
     namespace: 'Cogl',
     includes: ['GL-1.0', 'GObject-2.0'],
     dependencies: [cogl_deps],
-    extra_args: [
+    extra_args: introspection_args + [
       '-UCOGL_COMPILATION',
       '-D__COGL_H_INSIDE__',
       '-D__COGL_XLIB_H_INSIDE__',
       '-D__COGL_EGL_H_INSIDE__',
       '-D__COGL_GLX_H_INSIDE__',
       '-DCOGL_GIR_SCANNING',
-      '-U_GNU_SOURCE',
     ],
     install_dir_gir: pkglibdir,
     install_dir_typelib: pkglibdir,

meson.build

@@ -241,6 +241,11 @@ endif
 have_introspection = get_option('introspection')
 if have_introspection
   gobject_introspection_dep = dependency('gobject-introspection-1.0')
+
+  introspection_args = [
+    '--quiet',
+    '-U_GNU_SOURCE',
+  ]
 endif
 
 have_cogl_tests = get_option('cogl_tests')

src/meson.build

@@ -820,9 +820,7 @@ if have_introspection
       mutter_deps,
       libmutter_dep,
     ],
-    extra_args: mutter_c_args + [
-      '-U_GNU_SOURCE',
-    ],
+    extra_args: mutter_c_args + introspection_args,
     install_dir_gir: pkglibdir,
     install_dir_typelib: pkglibdir,
     install: true