Enable libcxx_static for Windows

- Use Win32 threads.  MinGW pthreads throws an error when building
libcxx since it's pthread_mutex_initializer is not constant (needs a
cast).
- Disable visibility annotations for libcxx and libcxxabi since we are
only going to support these as static libraries.
- Build sources for Windows platform support.
- Use SjLj exceptions for 32-bit.  libgcc_eh implements SjLj exception
model for 32-bit.
- Undefine WIN32_LEAN_AND_MEAN macro.  libcxx sources define them where
necessary.

Test: Build and test Windows binaries under Wine.

Change-Id: I76a440ff5d71eb5a3b7d57dd97e742a458ffbe16
1 file changed