azure-pipelines: Fix the fact that neither asan+ubsan were not actually enabled (#6428)

Also make the message about the unsupported value of LLVM_USE_SANITIZER
an error rather than a warning, so we don't make this mistake in the
future.

Author: amaiorano

azure-pipelines.yml

@@ -53,7 +53,7 @@ stages:
           configuration: Release
           CC: clang
           CXX: clang++
-          CMAKE_OPTS: -DLLVM_ENABLE_WERROR=On -DLLVM_USE_SANITIZER=Address,Undefined -DLLVM_ENABLE_LIBCXX=On -DLLVM_USE_LINKER=lld
+          CMAKE_OPTS: -DLLVM_ENABLE_WERROR=On -DLLVM_USE_SANITIZER='Address;Undefined' -DLLVM_ENABLE_LIBCXX=On -DLLVM_USE_LINKER=lld
           CHECK_ALL_ENV: ASAN_OPTIONS=alloc_dealloc_mismatch=0
           OS: Linux
         Linux_Clang_Debug:

cmake/modules/HandleLLVMOptions.cmake

@@ -535,13 +535,13 @@ if(LLVM_USE_SANITIZER)
       append("-fsanitize=address,undefined -fno-sanitize=vptr,function,alignment -fno-sanitize-recover=all"
               CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
     else()
-      message(WARNING "Unsupported value of LLVM_USE_SANITIZER: ${LLVM_USE_SANITIZER}")
+      message(FATAL_ERROR "Unsupported value of LLVM_USE_SANITIZER: ${LLVM_USE_SANITIZER}")
     endif()
   else()
     if (LLVM_USE_SANITIZER STREQUAL "Address")
       append("-fsanitize=address" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
     else()
-      message(WARNING "Unsupported value of LLVM_USE_SANITIZER: ${LLVM_USE_SANITIZER}")
+      message(FATAL_ERROR "Unsupported value of LLVM_USE_SANITIZER: ${LLVM_USE_SANITIZER}")
     endif()
   endif()
   if (LLVM_USE_SANITIZE_COVERAGE)