Add inhibit_stack_protector to ifuncmain9 [BZ #25680]

Enabling --enable-stack-protector=all causes the following tests to fail:

    FAIL: elf/ifuncmain9picstatic
    FAIL: elf/ifuncmain9static

Nick Alcock (who committed the stack protector code) marked the IFUNC
resolvers with inhibit_stack_protector when he done the original work and
suggested doing so again @ BZ #25680. This patch adds
inhibit_stack_protector to ifuncmain9.

After patch is applied, --enable-stack-protector=all does not fail the
above tests.

Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>

elf/ifuncmain9.c

@@ -43,6 +43,7 @@ implementation (void)
 }
 
 static __typeof__ (implementation) *
+inhibit_stack_protector
 resolver (void)
 {
   ++resolver_called;