Merge "Disable a warning that libc++'s headers trip." am: 1d29875829

am: b4e2a566f9

Change-Id: Iabee435286e7cd16d53899941f7c9832815e5dee

cc/config/clang.go

@@ -135,6 +135,9 @@ func init() {
 		// Turn off -Wthread-safety-negative, to avoid breaking projects that use -Weverything.
 		"-D_LIBCPP_ENABLE_THREAD_SAFETY_ANNOTATIONS",
 		"-Wno-thread-safety-negative",
+
+		// libc++'s math.h has an #include_next outside of system_headers.
+		"-Wno-gnu-include-next",
 	}, " "))
 
 	pctx.StaticVariable("ClangExtraTargetCflags", strings.Join([]string{