[Bug target/84371] test case gcc.target/powerpc/builtins-3.c fails on power9

[willschm at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84371

--- Comment #3 from Will Schmidt <willschm at gcc dot gnu.org> ---
(In reply to seurer from comment #1)
> In addition to trunk this also fails with gcc 7

Yup. 
There was/is an ice in one of the builtins-3.* tests that should be better now
, per https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84422#c1

it is in my queue to re-check the results, and possibly loosen up the requires
or options on one of the tests.  I'll pursue a backport to gcc7 after I check
that over.