i686: Compile .op files and gmon tests with -mfentry

i686: Compile .op files and gmon tests with -mfentry

On i686, after GCC 16 commit:

commit 07d8de9174c421d719649639a1452b8b9f2eee32
Author: H.J. Lu <hjl.tools@gmail.com>
Date:   Wed Jul 2 08:58:23 2025 +0800

    x86-64: Add --enable-x86-64-mfentry

which warns ‘-pg’ without ‘-mfentry’, when glibc is configured with
--disable-default-pie, GCC 16 fails to compile .op files and gmon tests
with error:

cc1: error: ‘-pg’ without ‘-mfentry’ may be unreliable with shrink wrapping [-Werror]

Compile .op files and gmon tests with -mfentry if it is supported by
CC/TEST_CC and glibc is configured with --disable-default-pie.  This
fixes BZ #33376.

Signed-off-by: H.J. Lu <hjl.tools@gmail.com>
Reviewed-by: Joseph Myers <josmyers@redhat.com>