ci: downgrade xcode to 12.5 for crossplatform tests
ci: downgrade xcode to 12.5 for crossplatform tests

mParticle/mparticle-apple-sdk,mParticle/mparticle-apple-sdk,mParticle/mparticle-apple-sdk,mParticle/mparticle-apple-sdk,mParticle/mparticle-apple-sdk,mParticle/mparticle-apple-sdk