Running jgit on Fedora >= 30 results in an immediate failure¹:
$ jgit --version
/usr/bin/build-classpath: Could not find xz-java Java extension for this JVM
/usr/bin/build-classpath: error: Some specified jars were not found
Error: Could not find or load main class org.springframework.boot.loader.JarLauncher
Skip the jgit tests if 'jgit --version' fails. This way we'll begin
running them again once the issue is resolved -- without having to make
any further changes to the git package.
Also exclude jgit on i386 arch, as upstream eclipse has dropped support.
We could adjust the conditional to only exclude on Fedora >= 30 and
i386, but the added complexity is not worth the effort.
¹ jgit bug report: https://bugzilla.redhat.com/1709624
