I get this error:
[34/46843] LIB obj/buildtools/third_party/libc++/libcpp.lib
FAILED: obj/buildtools/third_party/libc++/libcpp.lib
..\..\third_party\llvm-build\Release+Asserts\bin\lld-link.exe /lib /OUT:obj/buildtools/third_party/libc++/libcpp.lib /nologo /WX /ignore:4221 /llvmlibthin @obj/buildtools/third_party/libc++/libcpp.lib.rsp
warning: no input files, not writing output file
pass /llvmlibempty to write empty .lib file,
pass /ignore:emptyoutput to suppress warning
treating warning as error due to /WX