fix: Bail out on too hard MSVC environment variables CL and _CL_

fix: Bail out on too hard MSVC environment variables CL and _CL_

To handle the CL and _CL_ variables properly, ccache needs to parse them
according to [1] and then include the compiler options as part of
regular argument processing. Until that is done we have to bail out and
just run the original compiler.

[1]: https://docs.microsoft.com/en-us/cpp/build/reference/cl-environment-variables?view=msvc-170

Fixes #1022.