On my Enterprise Linux installation, the default "macrofiles" setup is
/usr/lib/rpm/macros:/usr/lib/rpm/%{_target}/macros:/etc/rpm/macros.specspo:/etc/rpm/macros.prelink:/etc/rpm/macros.solve:/etc/rpm/macros.up2date:/etc/rpm/macros:/etc/rpm/%{_target}/macros:~/.rpmmacros
I thought this meant that if I did
rpmbuild --target <something>
then /usr/lib/rpm/<something>/macros and /etc/rpm/<something>/macros
would be loaded (among other things), but based on experiments I just
did, it looks like this is not the case. [ ... ]
You can always use --define.
Replace %{_target} on your macrofiles setup for, say: %{customtag},
then:
rpmbuild --define 'customtag XXXX'