On Unicies `sys/stat.h` will provide `mkdir`. Windows provides the
POSIX requirement through the portable name `_mkdir` which is declared
in the `direct.h` header. This adds the additional header to the `ucrt`
module to allow access to this function.
Because Microsoft inlines the definitions of the printf family of
functions, we end up with undefined references to them. Add an explicit
request to link against the `legacy_stdio_definitions` library when
`ucrt.C.stdio` is used which provides out-of-line definitions for them.
This fixes the building of the `stdlib/VarArgs' test.
Since `stdin`, `stdout`, and `stderr` are defined via macros, we cannot see them
on the swift side. Replicate these by hand. Expose `STDIN_FILENO`,
`STDOUT_FILENO`, and `STDERR_FILENO` for compatibility with other libc
implementations. This reduces the need for changing the codebase unnecessarily
for MSVCRT.
This adds the swiftMSVCRT module which is similar in spirit to swiftGlibc and
swiftDarwin, exposing the Microsoft C Runtime library to swift. Furthermore,
disable pieces of the standard library which are not immediately trivially
portable to Windows. A lot of this functionality can still be implemented and
exposed to the user, however, this is the quickest means to a PoC for native
windows support.
As a temporary solution, add a -DCYGWIN flag to indicate that we are building
for the cygwin windows target. This allows us to continue supporting the cygwin
environment whilst making the windows port work natively against the windows
environment (msvc). Eventually, that will hopefully be replaced with an
environment check in swift.
