This replaces swiftMSVCRT with swiftCRT. The big difference here is
that the `visualc` module is no longer imported nor exported. The
`visualc` module remains in use for a singular test wrt availability,
but this should effectively remove the need for the `visualc` module.
The difference between the MSVCRT and ucrt module was not well
understood by most. MSVCRT provided ucrt AND visualc, combining pieces
of the old MSVCRT and the newer ucrt. The ucrt module is what you
really wanted most of the time, however, would need to use MSVCRT for
the convenience aliases for type-generic math and the deprecated math
constants.
Unfortunately, we cannot shadow the `ucrt` module and create a Swift SDK
overlay for ucrt as that seems to result in circular dependencies when
processing the `_Concurrency` module.
Although this makes using the C library easier for most people, it has a
more important subtle change: it cleaves the dependency on visualc.
This means that this enables use of Swift without Visual Studio for the
singular purpose of providing 3 header files. Additionally, it removes
the need for the installation of 2 of the 4 support files. This greatly
simplifies the deployment process on Windows.
Commit for CMake and build scripts to recognize OpenBSD. To keep this
commit relatively short, this just deals with the rather simple and
uncontroversial changes to the build system.
Note that OpenBSD calls "x86_64" as "amd64", Since the Swift stdlib will
be put in a subdirectory named after ARCH, to ensure the standard
library is properly found later, we use the native architecture name for
OpenBSD in the build system rather than trying to deal with the
difference the other way around.
There are situations where you want to build against a libc that is out
of tree or that is not the system libc (Or for cross build scenarios).
This is a change for passing the -sdk and include paths for things like
this.
The key thing here is that all of the underlying code is exactly the same. I
purposely did not debride anything. This is to ensure that I am not touching too
much and increasing the probability of weird errors from occurring. Thus the
exact same code should be executed... just the routing changed.
Create a new RuntimeUnittest library alongside the other stdlib unit
tests so we can write C++ runtime unit tests callable from lit.
Move runtime exclusivity tests into the stdlib unittest library and
create lit tests so we can verify that the runtime crashes with an
error message.
