Allow specifying CMake version or even local CMake Path on non-Win32 Platforms

[Naville]

In rare circumstances, it's required to use a specific version or even a specific installation of CMake

Environment

• For example, maccatalyst

To Reproduce
N/A

Expected behavior
N/A

Failure logs
N/A

Additional context

• Some NDA-restricted toolchain vendors also ship a customized CMake installation that has extra patches to allow building for that platforms
• For the non-NDA restricted part, Kitware/CMake@2785364 adds support to build for MacCatalyst, which is not shipped inside current vcpkg CMake version I believe

[Neumann-A]

Did you even try this out by putting a newer version than vcpkg requires on the PATH? Normally vcpkg only uses its internal version if there is no adequat version on PATH/installed or if the flag --x-abi-tools-use-exact-versions is used.