girepository: Move GIR generation into girepository and prior to tests

To enable tests which depend on libgirepository's GIR and typelib,
we need to refactor the order we're currently building these items.

We can also move everything under girepository/ to cleanup the
top-level.

girepository/meson.build

@@ -235,31 +235,7 @@ pkg.generate(libgirepository,
 )
 
 if enable_gir
-  libgirepository_gir_sources = [
-    gi_visibility_h,
-    girepo_headers,
-    girepo_sources,
-  ]
-  libgirepository_gir_packages = [ 'girepository-2.0' ]
-  libgirepository_gir_args = [
-    '-DGI_COMPILATION',
-    '--symbol-prefix=gi',
-    '--identifier-prefix=GI',
-  ]
-
-  girepository_gir = gnome.generate_gir(libgirepository,
-    sources: libgirepository_gir_sources,
-    namespace: 'GIRepository',
-    nsversion: '3.0',
-    identifier_prefix: 'GI',
-    symbol_prefix: 'gi',
-    export_packages: libgirepository_gir_packages,
-    header: 'girepository/girepository.h',
-    includes: [ glib_gir[0], gmodule_gir[0], gobject_gir[0], gio_gir[0] ],
-    install: true,
-    dependencies: [ libglib_dep, libgobject_dep, libgmodule_dep, libgio_dep ],
-    extra_args: gir_args + libgirepository_gir_args,
-  )
+  subdir('introspection')
 endif
 
 if build_tests