[Clang][Driver] Fix condition in combineBackendCompile when using -no-integrated-cpp (#136853)
When using -no-integrated-cpp, before, the driver won't collapse actions
when the input was not llvm-ir
or it would collapse them too aggressively with -save-temps
The original code was checking the action type (which is IR too for
preprocessed->bc actions) instead of the action inputs.