This change adds builtin_addressof_nocfi(). This built-in function
is similar to the existing builtin_addressof(), except that with
-fsanitize=cfi, it returns the address of the function body instead of
a CFI jump table address.
__builtin_addressof_nocfi() is helpful in low-level code, such as
operating system kernels, which may need the address of a specific
function without a jump table indirection.
Depends on D108478