release/18.x branch, commit 78b99c73ee4b96fe9ce0e294d4632326afb2db42
This adds the flag `-D_LIBCPP_HARDENING_MODE` which is determined based
on the Zig optimization mode.
This commit also fixes libunwind, libcxx, and libcxxabi to properly
report sub compilation errors.
also start prefering NtDll API. so far:
* NtQueryInformationFile
* NtClose
adds a performance workaround for windows unicode conversion. but that
should probably be removed before merging