The MinGW CRT wrapping has a few minor issues that makes native
TLS fail at the moment.
LLVM doesn't support native TLS on windows/aarch64, but emulated
TLS is supported now.
Dwarf is also the default in clang on i686, but libunwind currently
has an issue relating to unwinding dwarf exceptions on i686 on
windows (and less easily reproducible on other platforms),
see https://reviews.llvm.org/D38680.
This enables exceptions on aarch64, where they previously were
avoided/disabled.
When linking to a statically linked libunwind with support for
dwarf, one (currently) has to link in -lpsapi.
Martin Storsjö