CMake 3.18.3 broke Mac Make/Ninja builds for files with LANGUAGE OBJCXX that don't end with .mm extension
See the attached sample project. It contains two identical Objective C++ source files, one ending with .mm extension and one ending with .cpp extension (and LANGUAGE set to OBJCXX).
Using CMake 3.18.2 both of these files compile correctly with Make, Ninja, and Xcode generators. Using CMake 3.18.3 the .mm file compiles correctly with Make, Ninja, and Xcode generators. Using CMake 3.18.3 the .cpp file compiles correctly with Xcode, but not Make or Ninja.
From the verbose outputs I can see the
-x objective-c++ is no longer being passed to the compiler.