[clang] [clang] [Gnu] Improve GCCVersion parsing to match versions such as "10-win32" (PR #69079)

[Martin Storsjö via cfe-commits]

mstorsjo wrote:

This goes on top of #69078 - the first commit is reviewed there, thus within this PR, only review the second commit on its own.

https://github.com/llvm/llvm-project/pull/69079