TestMultilibBlueprintDepsolveV0 unit test relies on 'gsl' package and
the availability of its 32 bit and 64 bit versions in the distribution
repositories. However, the package is no longer available in c10s /
el10. Moreover, there are no 32 bit RPMs in the repositories.
Conditionally compile the test only if 'rhel10' build tag is not
specified. Modify the SPEC file to define 'rhelX' build tag when
compiling tests on RHEL, where X is the major version.
Signed-off-by: Tomáš Hozza <thozza@redhat.com>