Escape 'gomadir' for GN.

No real functionality change (except for people who have " or $ in their gomadir,
but since that didn't work up until this change nobody does that).

R=brettw@chromium.org

Review URL: https://codereview.chromium.org/140123003

git-svn-id: http://src.chromium.org/svn/trunk/src/build@245799 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

gyp_chromium

@@ -207,7 +207,7 @@ def GetArgsStringForGN(supplemental_files):
 
   # gomadir is renamed goma_dir in the GN build.
   if 'gomadir' in vars_dict:
-    gn_args += ' goma_dir="%s"' % vars_dict['gomadir']
+    gn_args += ' goma_dir=%s' % EscapeStringForGN(vars_dict['gomadir'])
 
   # These arguments get passed directly as integers (avoiding the quoting and
   # escaping of the string ones above).