Suppress -Wnonportable-include-path on clang tot bots

BUG=617318
R=hans@chromium.org

Review URL: https://codereview.chromium.org/2040533003 .

Cr-Original-Commit-Position: refs/heads/master@{#397823}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 2bc751024e4ddf3f50594abdbf3c54b77df84562

common.gypi

@@ -3060,6 +3060,10 @@
         # TODO: Enable on Windows too, http://crbug.com/404525
         'variables': { 'clang_warning_flags': ['-Wexit-time-destructors']},
       }],
+      ['"<!(python <(DEPTH)/tools/clang/scripts/update.py --print-revision)"!="270823-1"', {
+        # TODO(thakis): https://crbug.com/617318
+        'variables': { 'clang_warning_flags': ['-Wno-nonportable-include-path']},
+      }],
       ['chromium_code==0', {
         'variables': {
           'clang_warning_flags': [

config/compiler/BUILD.gn

@@ -1005,6 +1005,13 @@ config("default_warnings") {
         # TODO(thakis): https://crbug.com/604888
         "-Wno-undefined-var-template",
       ]
+
+      if (llvm_force_head_revision) {
+        cflags += [
+          # TODO(thakis): https://crbug.com/617318
+          "-Wno-nonportable-include-path",
+        ]
+      }
     }
   }
 }