Ignored errors in cross-compiled build jobs

Currently, all ppc64le and s390x kernel-ark build jobs contain two kinds of ignored errors that should be properly fixed and not ignored.

example:

• [redhat] configs: Disable CONFIG_XFS_SUPPORT_V4 (!2916 - merged)
• ELN MR pipeline: https://gitlab.com/redhat/red-hat-ci-tools/kernel/cki-internal-pipelines/cki-trusted-contributors/-/pipelines/1161426202
• ppc64le build job, build log
• s390x build job, build log

first failure (cc1)

00:00:23 + /usr/bin/make CROSS_COMPILE=ppc64le-linux-gnu- -s HOSTCFLAGS= HOSTLDFLAGS= ARCH=powerpc 'KCFLAGS= ' WITH_GCOV=0 -j24 vmlinux
00:00:27 cc1: error: bad value ‘power9’ for ‘-mtune=’ switch

00:00:22 + /usr/bin/make CROSS_COMPILE=s390x-linux-gnu- -s HOSTCFLAGS= HOSTLDFLAGS= ARCH=s390 'KCFLAGS= ' WITH_GCOV=0 -j24 bzImage
00:00:25 cc1: error: bad value ‘z14’ for ‘-march=’ switch

second failure (objcopy)

00:14:02 + /usr/bin/find-debuginfo -j24 --strict-build-id -n -i -r -q --keep-section .BTF -p '.*/usr/src/kernels/.*|XXX' -o ignored-debuginfo.list -p '/.*/6.8.0-0.rc2.6764c317b6bb.21.test.eln.ppc64le/.*|/.*6.8.0-0.rc2.6764c317b6bb.21.test.eln.ppc64le(.debug)?' -o debuginfo.list /tmp/rpmbuild/BUILD/kernel-6.8.0-0.rc2.6764c317b6bb.21.test
00:14:08 objcopy: Unable to recognise the format of the input file `/tmp/rpmbuild/BUILDROOT/kernel-6.8.0-0.rc2.6764c317b6bb.21.test.eln.ppc64le/lib/modules/6.8.0-0.rc2.6764c317b6bb.21.test.eln.ppc64le/internal/drivers/gpu/drm/tests/drm_managed_test.ko'

00:05:02 + /usr/bin/find-debuginfo -j24 --strict-build-id -n -i -r -q --keep-section .BTF -p '.*/usr/src/kernels/.*|XXX' -o ignored-debuginfo.list -p '/.*/6.8.0-0.rc2.6764c317b6bb.21.test.eln.s390x/.*|/.*6.8.0-0.rc2.6764c317b6bb.21.test.eln.s390x(.debug)?' -o debuginfo.list /tmp/rpmbuild/BUILD/kernel-6.8.0-0.rc2.6764c317b6bb.21.test
00:05:05 objcopy: objcopy: Unable to recognise the format of the input file `/tmp/rpmbuild/BUILDROOT/kernel-6.8.0-0.rc2.6764c317b6bb.21.test.eln.s390x/lib/modules/6.8.0-0.rc2.6764c317b6bb.21.test.eln.s390x/internal/drivers/base/test/property-entry-test.ko'