[build][cleanup] Use relative path to files

Eliminating absolute paths to outputs unlocks potential to remote
build with caching.

Bug: 92670
Change-Id: I474608d7e897811acb92894cf91691e60cc66a42
diff --git a/compiled_js.gni b/compiled_js.gni
index a2e13ed..c8ace40 100644
--- a/compiled_js.gni
+++ b/compiled_js.gni
@@ -30,7 +30,7 @@
     args = [
       "-c",
       "-o",
-      rebase_path(generated_file),
+      rebase_path(generated_file, root_build_dir),
     ]
     if (defined(invoker.module) && invoker.module) {
       args += [ "-m" ]