[gjs] build: Use pch header for the internal library

[Philip Chimento <pchimento src gnome org>]

commit 24f635e72bcfee4bc2dc36a4105013b10e77cefb
Author: Marco Trevisan (Treviño) <mail 3v1n0 net>
Date:   Wed May 19 19:09:57 2021 +0200

    build: Use pch header for the internal library
    
    This was supposed to happen since the start, but got lost in a previous
    rebase, so use precompiled headers to compile the main internal library.

 meson.build | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/meson.build b/meson.build
index 15701d47..253cdbbd 100644
--- a/meson.build
+++ b/meson.build
@@ -523,6 +523,7 @@ libgjs_jsapi = static_library(meson.project_name() + '-jsapi',
 # library so that we compile its sources just once.
 libgjs_internal = static_library('gjs-internal',
     libgjs_sources, probes_header, probes_objfile,
+    cpp_pch: pch_headers,
     dependencies: base_build_dep,
     link_with: libgjs_jsapi)