From
https://build.chromium.org/p/chromium.fyi/builders/ClangToTMac/builds/14987:

FAILED: lib/ubsan/CMakeFiles/RTUbsan.ios.dir/ubsan_handlers.cc.o 
/Applications/Xcode8.0.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/c++    -I/b/c/builder/ClangToTMac/src/third_party/llvm/compiler-rt/lib/ubsan/.. -DLLVM_FORCE_HEAD_REVISION -Wall -std=c++11 -Wno-unused-parameter -O3 -DNDEBUG -arch armv7 -arch armv7s -arch arm64 -arch armv7k -isysroot /Applications/Xcode8.0.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.12.sdk    -DLLVM_FORCE_HEAD_REVISION -Wall -std=c++11 -Wno-unused-parameter -stdlib=libc++ -miphoneos-version-min=8.0 -isysroot /Applications/Xcode8.0.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS10.0.sdk -fPIC -fno-builtin -fno-exceptions -funwind-tables -fno-stack-protector -fno-sanitize=safe-stack -fvisibility=hidden -fvisibility-inlines-hidden -fno-lto -O3 -gline-tables-only -Wno-gnu -Wno-variadic-macros -Wno-c99-extensions -Wno-non-virtual-dtor -frtti -MMD -MT lib/ubsan/CMakeFiles/RTUbsan.ios.dir/ubsan_handlers.cc.o -MF lib/ubsan/CMakeFiles/RTUbsan.ios.dir/ubsan_handlers.cc.o.d -o lib/ubsan/CMakeFiles/RTUbsan.ios.dir/ubsan_handlers.cc.o -c /b/c/builder/ClangToTMac/src/third_party/llvm/compiler-rt/lib/ubsan/ubsan_handlers.cc
/b/c/builder/ClangToTMac/src/third_party/llvm/compiler-rt/lib/ubsan/ubsan_handlers.cc:675:13: error: static declaration of '__ubsan_handle_cfi_bad_type' follows non-static declaration
static void __ubsan_handle_cfi_bad_type(CFICheckFailData *Data,
            ^
/b/c/builder/ClangToTMac/src/third_party/llvm/compiler-rt/lib/ubsan/ubsan_handlers.h:198:47: note: previous declaration is here
extern "C" SANITIZER_INTERFACE_ATTRIBUTE void __ubsan_handle_cfi_bad_type(
                                              ^
1 error generated.



Last good:
https://build.chromium.org/p/chromium.fyi/builders/ClangToTMac/builds/14939
First bad:
https://build.chromium.org/p/chromium.fyi/builders/ClangToTMac/builds/14940



I'm guessing this is due to r313391.