Merge branch 'cb/ci-make-p4-optional'

macOS CI jobs have been occasionally flaky due to tentative version skew between perforce and the homebrew packager. Instead of failing the whole CI job, just let it skip the p4 tests when this happens. * cb/ci-make-p4-optional: ci: use https, not http to download binaries from perforce.com ci: reintroduce prevention from perforce being quarantined in macOS ci: avoid brew for installing perforce ci: make failure to find perforce more user friendly