[vcpkg_configure_make] Automatically convert paths in all options that contain Windows format on Windows

[JackBoosY]

Since vcpkg_*_make is used in Windows to use the minGW cross-compilation environment, the path included in all options must be in unix format at this time.
Add automatic conversion code to prevent parameters in the wrong format from being passed in.

Here are some reasons why it was modified here:

1. Using mingW bundled cygpath to convert the path is more appropriate and safer than using string(REGEX).
2. At present, we only know that icu has this issue, and we don’t know and it is easy to ignore whether other ports and PRs also have such issues.
3. Make sure that the path is in unix format should be something that the vcpkg tool function needs to do, not something that needs to be considered in portfile.cmake.

Related: #19726
Fixes #18086.

[JackBoosY]

I can separate this part into a new vcpkg function in a new cmake file so that portfile.cmake can be called if needed.

[dg0yt]

Since vcpkg_*_make is used in Windows to use the minGW cross-compilation environment, the path included in all options must be in unix format at this time.

I don't think the situation is so clear. I see two major issues:

• vcpkg uses msys2 which does automatic path conversions (though not perfectly) for command line paramaters and for environment variables when entering and leaving subsystems.
• In some cases, paths will be passed to Windows tools, or written to files used by Windows tools. These tools do need Windows paths.

[JackBoosY]

@dg0yt Yeah, if the path is only passed to the tool, yes. And we can't judge the function of the parameter inside vcpkg_configure_make.
So how about separate the convert path to a new vcpkg function and check Windows path in vcpkg_configure_make, then print warning message only?

[dg0yt]

So how about separate the convert path to a new vcpkg function and check Windows path in vcpkg_configure_make, then print warning message only?

I would appreciate a single function (or a set of functions) for msys path conversion instead of proliferating path conversion code over multiple consuming scripts. But when you want to use cygpath, you need a MSYS_ROOT. I still miss a good strategy on how to limit the number of roots. (We already have a second msys root for pkg-config.)

I don't like so much the idea of adding a warning message when it is unlikely to indicate an actual issue. AFAIK there is no actual issue besides icu ATM. Msys path conversion seems to do the right thing most of the time.

[dg0yt]

But when you want to use cygpath, you need a MSYS_ROOT.

And of course you need the matching cygpath for config/build.

[JackBoosY]

So we prefer to use #19726 instead of this.