Attempting to build LVM2 fails as http://sources.redhat.com/ is completely down. In my environment, I updated the LVM link to https://sourceware.org/ftp/lvm2/ and updated the hash which fixed the problem and allowed my filesystem to build.
Fixed by https://git.buildroot.org/buildroot/commit/?id=130cfc74d7a273999a3e61100a75d8ac1acc3579, thanks