These should hopefully all be uncontroversial, minimal changes to deal
with progressing the build to completion on OpenBSD or addressing minor
portability issues. This is not the full set of changes to get a
successful build; other portability issues will be addressed in future
commits.
Most of this is just adding the relevant clauses to the ifdefs, but of
note in this commit:
* StdlibUnittest.swift: the default conditional in _getOSVersion assumes
an Apple platform, therefore the explicit conditional and the relevant
enums need filling out. The default conditional should be #error, but
we'll fix this in a different commit.
* tgmath.swift.gyb: inexplicably, OpenBSD is missing just lgammal_r.
Tests are updated correspondingly.
* ThreadLocalStorage.h: we use the pthread implementation, so it
seems we should typedef __swift_thread_key_t as pthread_key_t.
However, that's also a tweak for another commit.
We use one bit of the third reserved swift private tls key.
Also move the functionality into a separate static archive that is
always linked dependent on deployment target.
The mapping of the return value of the `FlsAlloc` was flipped resulting
in the failure of the TLS key creation. The test suite would fail to
generate the TLS key resulting in failures.
Fix syntactic issues in the swift runtime build from the recent TLS changes.
Move the helper definitions into the TLS stubs rather than emitting them
everywhere. This allows the runtime to build again on Windows.
