girepository: Update gi-compile-repository and use it to compile GIRs

Adapt gi-compile-repository sources to compile against the updated
libgirepository that is included with GLib.

This also renames "g-ir-compiler" to "gi-compile-repository" to avoid
overwriting the existing binary and to simplify the binary name going
forward.

girepository/meson.build

@@ -241,3 +241,5 @@ endif
 if build_tests
   subdir('tests')
 endif
+
+subdir('compiler')