Update action.yml

Author: mcbarton

.github/actions/Build_and_Test_cppyy/action.yml

@@ -152,8 +152,8 @@ runs:
         cd ..\cppyy-backend\build\
         # Build and Install cppyy-backend
         $env:INCLUDE=$env:CPLUS_INCLUDE_PATH
-        $env:CC=cl.exe
-        $env:CXX=cl.exe
+        $env:CC="cl.exe"
+        $env:CXX="cl.exe"
         cmake -DCppInterOp_DIR=$env:CPPINTEROP_DIR -G Ninja ..
         ninja -v
         cp libcppyy-backend.dll $env:CPPINTEROP_DIR\lib\