Different tests used different os checks for importing Darwin, Glibc and
MSVCRT. This commit use the same pattern for importing those libraries,
in order to avoid the #else branches of the incorrect patterns to be
applied to the wrong platform. This was very normal for Android, which
normally should follow the Linux branches, but sometimes was trying to
import Darwin or not importing anything.
The standarized pattern imports Darwin for macOS, iOS, tvOS and watchOS.
It imports Glibc for Linux, FreeBSD, PS4, Android, Cygwin and Haiku; and
imports MSVCRT for Windows. If a new platform is introduced, the else
branch will report an error, so the new platform can be added to one of
the branches (or maybe add a new specific branch).
In some cases the standard pattern was modified because some test required
it (importing extra modules, or extra type aliases), and in some other
cases some branches were removed because the test will not have used
them (but it is not exhaustive, so there might be some unnecessary
branches).
This should, at least, fix three tests for Android (the three
dynamic_replacement*.swift ones).
This adjusts the standard library test suite to mostly pass on Windows.
The remaining failures are due to various cases:
- memory corruption (`_swift_stdlib_free` in swiftDemangle)
- heap corruption (canGrowUsingRealloc)
- withVAList failure (unresolved)
- unicode handling on the command line
Android differs in subtle ways from Linux. For example sem_open is
completely unimplemented, and always returns ENOSYS. None of the
test using sem_open were going to work.
Additionally the l_len field of the flock struct is typed as
__kernel_off_t, which doesn't have the same size as off_t.
Finally, the current working directory is always /, so creating
relative files will fail. We have to find the executable directory
and create the file there.
