[pstl] Add a __pstl_config_site header to record the CMake configuration

This commit adds a __pstl_config_site header that contains the value of
macros specified at CMake configuration time. It works similarly to
libc++'s __config_site header, except we always include it as a separate
file instead of concatenating it to the main configuration header.

It is necessary to thread the includes for that header into libc++'s
lit configuration, otherwise we'd be requiring an installation step
prior to running the test suite.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@368284 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed