Fix mac builds ... once again
Fix mac builds ... once again

Apparently, xcode 14 has a reported linker bug which prevents a
successful build. The recommended workaround is to revert toolchain to
last known good version (v13.4.1). More information can be found here -

https://github.com/actions/runner-images/issues/6350

Also, when macos-latest is used, CI can use either macos11 or macos12
and the build fails if it selects the former. Enforce macos-12 strictly
for now.

alainmarcel/Surelog,chipsalliance/Surelog,chipsalliance/Surelog,alainmarcel/Surelog,chipsalliance/Surelog,alainmarcel/Surelog,chipsalliance/Surelog,alainmarcel/Surelog