Improve mingw link flag handling

[dzbarsky]

Without this, we get errors like

          lld: error: unable to find library -lliblibcxx.static
          lld: error: unable to find library -lliblibcxxabi.static
          lld: error: unable to find library -lliblibunwind.static
          lld: error: unable to find library -llibmingw32
          lld: error: unable to find library -llibucrtbase

because get_lib_windows doesn't strip the leading lib.

non-msvc mode should use the same lib-naming conventions as non-windows.

[UebelAndre]

Thanks! I take it you have a mingw toolchain you're developing with? Can you check if there's a unit test for this that also needs to be updated? I feel like there is but don't remember where off hand.

[UebelAndre]

I'd prefer not to pin this here if possible.

[dzbarsky]

I'll revert this bit before landing; this was to debug the coverage duplicate actions that broke in bazel 8.5 and is another cause of red CI currently. bazelbuild/bazel#28056

[dzbarsky]

Thanks! I take it you have a mingw toolchain you're developing with? Can you check if there's a unit test for this that also needs to be updated? I feel like there is but don't remember where off hand.

Yes we added hermetic mingw support to https://github.com/cerisier/toolchains_llvm_bootstrapped

I don't think there's a unit test for this, everything is green when run locally.

Tests can surely be added but given how many fixes I need to do here to get things functional, I don't know if I have cycles for adding all of them, they're a bit annoying to setup