Handle the case where LLVM_REVISION is undefined (due to LLVM_APPEND_VC_REV=OFF or otherwise) by setting "<unknown>" value as before D123549. Reviewed By: yota9 Differential Revision: https://reviews.llvm.org/D123852
Handle the case where LLVM_REVISION is undefined (due to LLVM_APPEND_VC_REV=OFF or otherwise) by setting "<unknown>" value as before D123549. Reviewed By: yota9 Differential Revision: https://reviews.llvm.org/D123852