[Bug testsuite/78740] test case powerpc/pr78691-ppc.c fails starting with its introduction in r243335

[wschmidt at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78740

--- Comment #4 from Bill Schmidt <wschmidt at gcc dot gnu.org> ---
Since the test doesn't have a { dg-do ... }, I don't know whether you were
intending compile-only or an executable test.  Use { dg-do run { target ... } }
as needed.