Bug 1747879 - Pass Thunderbird subrepo srcpath to symbolstore.py. r=firefox-build-system-reviewers,andi,a=dsmith

The sym files generated for Thunderbird builds contain incorrect VCS references.
symbolstore.py will handle the subrepo correctly with an additional -s argument
if MOZ_SOURCE_REPO and MOZ_SOURCE_CHANGESET are not set. See D135392.

Differential Revision: https://phabricator.services.mozilla.com/D135299

python/mozbuild/mozbuild/action/dumpsymbols.py

@@ -57,6 +57,9 @@ def dump_symbols(target, tracking_file, count_ctors=False):
     if objcopy:
         os.environ["OBJCOPY"] = objcopy
 
+    if buildconfig.substs.get("MOZ_THUNDERBIRD"):
+        sym_store_args.extend(["-s", os.path.join(buildconfig.topsrcdir, "comm")])
+
     args = (
         [
             sys.executable,