Don't add optnone or noinline if the function is already marked as

always_inline.

The assertion in SetLLVMFunctionAttributesForDefinition used to fail
when there was attribute OptimizeNone on the AST function and attribute
always_inline on the IR function. This happens because base destructors
are annotated with always_inline when the code is compiled with
-fapple-kext (see r124757).

rdar://problem/57169694