https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89929
--- Comment #7 from H.J. Lu <hjl.tools at gmail dot com> ---
__attribute__((target("foo"))) can be used in 2 different ways:
1. Enable FOO, which works for both C and C++.
2. Function versioning with FOO, which works only for C++.
2 is a subset of 1. We should improve error message when target
is in 1, but outside of 2.
