s390: Add -fno-stack-protector to 3 tests

In Fedora/RHEL we usually test with
make check RUNTESTFLAGS="--target_board=unix/'{,-fstack-protector-strong}'"
because -fstack-protector-strong is used when building pretty much all the
packages.

In the past Marek Polacek has committed tweaks to various tests to make
them PASS in such testing, see e.g. r14-6276 or r14-2200.
These 3 tests FAIL with -fstack-protector-strong on s390x because they
use check-function-bodies and aren't prepared for the extra
-fstack-protector-{strong,all} extra code in the prologue/epilogue.

The following patch should fix that.

2025-07-01  Jakub Jelinek  <jakub@redhat.com>

	* gcc.target/s390/vector/vec-abs-emu.c: Add -fno-stack-protector
	to dg-options.
	* gcc.target/s390/vector/vec-max-emu.c: Likewise.
	* gcc.target/s390/vector/vec-min-emu.c: Likewise.

(cherry picked from commit 01564529234461d84c7df1b0223fd908d8bcbfee)