When building protos, also check if CMAKE_CROSSCOMPILING is set, (#7351)
When building protos, also check if CMAKE_CROSSCOMPILING is set, (#7351)

which is the case when building for arm64 on an x64 mac or vice versa.
firebase/firebase-ios-sdk,firebase/firebase-ios-sdk,firebase/firebase-ios-sdk,firebase/firebase-ios-sdk,firebase/firebase-ios-sdk,firebase/firebase-ios-sdk,firebase/firebase-ios-sdk