We patch girdir and typelibdir in gobject-introspection to include pc_sysrootdir
for cross compiling.
Avoid using pkg-config variables for girdir_for_pc_file and typelibdir_for_pc_file
since they include pc_sysrootdir, which cannot be overridden using pkgconfig_define.
meson needs non-absolute paths in order to correctly generate datadir.
--- a/meson.build
+++ b/meson.build
@@ -96,9 +96,9 @@ typelibdir_for_pc_file = join_paths('${libdir}', 'girepository-1.0')
 gobject_introspection = dependency('gobject-introspection-1.0', required: false)
 if gobject_introspection.found()
     girdir = gobject_introspection.get_variable(pkgconfig: 'girdir', pkgconfig_define: ['datadir', datadir])
-    girdir_for_pc_file = gobject_introspection.get_variable(pkgconfig: 'girdir', pkgconfig_define: ['datadir', '${datadir}'])
+    girdir_for_pc_file = join_paths('${datadir}', 'gir-1.0') 
     typelibdir = gobject_introspection.get_variable(pkgconfig: 'typelibdir', pkgconfig_define: ['libdir', libdir])
-    typelibdir_for_pc_file = gobject_introspection.get_variable(pkgconfig: 'typelibdir', pkgconfig_define: ['libdir', '${libdir}'])
+    typelibdir_for_pc_file = join_paths('${libdir}', 'girepository-1.0')
 endif
 
 vapidir = join_paths(datadir, 'vala', 'vapi')