ninja: Entering directory `out/gn'
[1/3] ACTION //libcxx/include:write_modulemap(//llvm/utils/gn/build/toolchain:unix)
[2/3] COPY ../../libcxx/include/flat_map include/c++/v1/flat_map
[3/3] COPY ../../libcxx/include/flat_set include/c++/v1/flat_set