[introspection] Skip sources not usable with GObject Introspection

There is no point in generating GIR for code interfacing with libraries
without introspection integration. This fixes spurious warnings on macOS
when g-ir-scanner mistakenly tries to scan system headers.

src/meson.build

@@ -431,6 +431,18 @@ if conf.get('HAVE_FREETYPE', 0) == 1
   hb_features.set('HB_HAS_FREETYPE', 1)
 endif
 
+if conf.get('HAVE_GLIB', 0) == 1
+  hb_sources += hb_glib_sources
+  hb_headers += hb_glib_headers
+  harfbuzz_deps += [glib_dep]
+  hb_features.set('HB_HAS_GLIB', 1)
+endif
+
+# We set those here to not include the sources below that are of no use to
+# GObject Introspection
+gir_sources = hb_sources + hb_gobject_sources
+gir_headers = hb_headers + hb_gobject_headers
+
 if conf.get('HAVE_GDI', 0) == 1
   hb_sources += hb_gdi_sources
   hb_headers += hb_gdi_headers
@@ -445,13 +457,6 @@ if conf.get('HAVE_GRAPHITE2', 0) == 1
   hb_features.set('HB_HAS_GRAPHITE', 1)
 endif
 
-if conf.get('HAVE_GLIB', 0) == 1
-  hb_sources += hb_glib_sources
-  hb_headers += hb_glib_headers
-  harfbuzz_deps += [glib_dep]
-  hb_features.set('HB_HAS_GLIB', 1)
-endif
-
 if conf.get('HAVE_UNISCRIBE', 0) == 1
   hb_sources += hb_uniscribe_sources
   hb_headers += hb_uniscribe_headers
@@ -816,7 +821,7 @@ if have_gobject
   if build_gir
     conf.set('HAVE_INTROSPECTION', 1)
     hb_gen_files_gir = gnome.generate_gir(libharfbuzz_gobject,
-      sources: [hb_headers, hb_sources, hb_gobject_headers, hb_gobject_sources, enum_h],
+      sources: [gir_headers, gir_sources, enum_h],
       dependencies: libharfbuzz_dep,
       namespace: 'HarfBuzz',
       nsversion: '0.0',