[CMake] Fix handling of passing through semi-colon separated lists.

When passing around CMake arguments as lists of arguments any arguments containing lists need to have their semi-colons escaped otherwise CMake will split the arguments in the middle.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@253720 91177308-0d34-0410-b5e6-96231b3b80d8