That's a partial fix for https://github.com/llvm/llvm-project/issues/55292.
Before, known builtins behaved differently from other identifiers:
void f () { return F (__builtin_LINE() + __builtin_FOO ()); }
After:
void f () { return F (__builtin_LINE () + __builtin_FOO ()); }
Any identifiers and keywords are covered now.