objdump, objcopy and strip are not used from the cross-compile toolchain for the target architecture
When cross-compiling kernel and kernel-tools for RHEL 8.6 using cross-compiler in builder-rhel8.6:production container, such errors are returned:
objcopy: Unable to recognise the format of the input file `/cki/rpmbuild/BUILDROOT/kernel-4.18.0-372.86.1.el8_6.6022_1112394150.s390x/lib/modules/4.18.0-372.86.1.el8_6.6022_1112394150.s390x+zfcpdump/vdso/vdso64.so'
00:03:17 /usr/bin/strip: Unable to recognise the format of the input file `/tmp/rpmbuild/BUILDROOT/kernel-4.18.0-372.86.1.el8_6.6022_1112394150.s390x/usr/libexec/ksamples/bpf/tcp_synrto_kern.o'
This is because objcopy and strip are run without the cross-compiling prefix. Tools without prefix on the system do not support architectures other than host's.
Resolve the issue, so that those errors do not occur.
Bug report to RPM developers: RHEL-21797.