Failing build: https://build.chromium.org/p/chromium.fyi/builders/ClangToTWinThinLTO64/builds/5

Logs: https://luci-logdog.appspot.com/v/?s=chromium%2Fbb%2Fchromium.fyi%2FClangToTWinThinLTO64%2F5%2F%2B%2Frecipes%2Fsteps%2Fcompile%2F0%2Fstdout

Excerpt:
[1592/51773] LINK(DLL) ppapi_example_simple_font.dll ppapi_example_simple_font.dll.lib ppapi_example_simple_font.dll.pdb
FAILED: ppapi_example_simple_font.dll ppapi_example_simple_font.dll.lib ppapi_example_simple_font.dll.pdb 
C:/b/depot_tools/win_tools-2_7_6_bin/python/bin/python.exe ../../build/toolchain/win/tool_wrapper.py link-wrapper environment.x64 False ../../third_party/llvm-build/Release+Asserts/bin/lld-link.exe /nologo /IMPLIB:./ppapi_example_simple_font.dll.lib /DLL /OUT:./ppapi_example_simple_font.dll /PDB:./ppapi_example_simple_font.dll.pdb @./ppapi_example_simple_font.dll.rsp
Warning: request a ThreadPool with 8 threads, but LLVM_ENABLE_THREADS has been turned off
LLVM ERROR: Failed to open cache file thinlto-cache\llvmcache-E51AFE4AAC64B870ABBFB4F3545F45E82C4169F5: permission denied