https://developercommunity.visualstudio.com/t/warning-C5287:-operands-are-different-e/10877942?

It is not able to silence "operands are different enum types"
warnings, even using an explicit cast, as the message says.

```
x64-vcruntime140-ruby350.def : error LNK2001: unresolved external symbol Avx2WmemEnabledWeakValue
```

	Fix redefinition of `clock_gettime` and `clock_getres`

	winpthreads-git 12.0.0.r720 provides `clock_gettime` and
	`clock_getres` as inline functions.

	digest.so needs ruby/digest.h which is installed by build-ext

	Copy to path with the base name

This change will be merged into 3.5 along with other encoding, command
line, environment variables, etc.

Revert following commits:

- bd831bcca534955533d9135d8c2f22d7ae5b9aa8
  [Bug #20929] Win32: Use `wcsftime`

- 1c15f641cc2bb88fa88123a11036ed58fbf9aa6d
  [Bug #20929] Win32: Encode timezone name in UTF-8

- 78762b52185aa80ee55c0d49b495aceed863dce2
  [Bug #20929] Fix `assert_zone_encoding`

1. Store the `PKG_CONFIG` variable in Makefile.sub (or try to get it from the ENV var PKG_CONFIG in mkmf.rb)
2. Try to use --msvc-syntax, with a fallback to replacing -Lxxx with -libpath:xxx. --msvc-syntax has been in pkgconf since 1.4.0 (released 7 years ago). pkg-config (freedesktop), does not support it, hence the fallback.
3. The `try_ldflags` passes these `ldflags` as the `opt` parameter to the `link_command`, not as `ldflags`. Unix systems are forgiving in that regard, MSVC is not: as a result as passing them as `opt`, they (specifically the `/libpath:xxx` ones) end up passed before the `-link` command to `cl.exe` and it throws because it ignores it and therefore can't find the lib.

```
cl : Command line warning D9002 : ignoring unknown option '-libpath:C:/Users/julien/.conan2/p/libff3726d89a6255c/p/lib'
```

Such as `$(ruby_version)`, `$(arch)` and so on.