packaging: enable rust extensions on centos Test on CentOS 7, repository with ~170000 tracked files, no untracked files: 10 runs with this enabled: -- Run #0 time: 0.6519973278045654 -- Run #1 time: 0.6933724880218506 -- Run #2 time: 0.7512078285217285 -- Run #3 time: 0.7517638206481934 -- Run #4 time: 0.5966529846191406 -- Run #5 time: 0.5960886478424072 -- Run #6 time: 0.5940573215484619 -- Run #7 time: 0.5963726043701172 -- Run #8 time: 0.6048009395599365 -- Run #9 time: 0.603604793548584 10 runs without this enabled: -- Run #0 time: 2.127584457397461 -- Run #1 time: 2.066192865371704 -- Run #2 time: 2.0831892490386963 -- Run #3 time: 2.077716588973999 -- Run #4 time: 2.07608962059021 -- Run #5 time: 2.072899341583252 -- Run #6 time: 2.094369888305664 -- Run #7 time: 2.067504644393921 -- Run #8 time: 2.069610834121704 -- Run #9 time: 2.0567898750305176 Differential Revision: https://phab.mercurial-scm.org/D9294