Update aosp/master Clang for rebase to r275480

Bug: http://b/31320715

This merges commit ac9cc4764cf47a6c3f031687d8592e080c9f5001 from
aosp/dev.

Test: Build AOSP and run RenderScript tests (host tests for slang and
libbcc, RsTest, CTS)

Change-Id: Ic2875e5c3673c83448cd7d1013861e42947b1b55
diff --git a/lib/Driver/CrossWindowsToolChain.cpp b/lib/Driver/CrossWindowsToolChain.cpp
index 57bf896..4ebbc53 100644
--- a/lib/Driver/CrossWindowsToolChain.cpp
+++ b/lib/Driver/CrossWindowsToolChain.cpp
@@ -62,6 +62,8 @@
     llvm::sys::path::append(ResourceDir, "include");
     addSystemInclude(DriverArgs, CC1Args, ResourceDir);
   }
+  for (const auto &P : DriverArgs.getAllArgValues(options::OPT_isystem_after))
+    addSystemInclude(DriverArgs, CC1Args, P);
   addExternCSystemInclude(DriverArgs, CC1Args, SysRoot + "/usr/include");
 }