FindMatlab: Silence warnings for mex version file

This adds -w for compilers supported by Matlab and clang to the source file's compile options.

Note: I also implemented an alternative, more generic approach in #24851 (comment 1478222) which I discarded due to its 'hackish' nature.

Fixes: #24851 (closed)
Topic-rename: findmatlab-silence-mex-warnings