Roll DEPS for gyp to r1921

Changes:
  r1921: Fix link step when specifying CLANG_CXX_LIBRARY
  r1920: Don't exclude sources for 'none' targets

BUG=366744

Review URL: https://codereview.chromium.org/297473002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@271657 0039d316-1c4b-4281-b951-d872f2087c98

DEPS

@@ -149,7 +149,7 @@ deps = {
     (Var("googlecode_url") % "grit-i18n") + "/trunk@167",
 
   "src/tools/gyp":
-    (Var("googlecode_url") % "gyp") + "/trunk@1919",
+    (Var("googlecode_url") % "gyp") + "/trunk@1921",
 
   "src/tools/swarming_client":
     Var("chromium_git") + "/external/swarming.client.git@" +