add jemalloc library

[libert-xyz]

jemalloc is quite popular these days and we should add the availability to configure like:

./configure --with-jemalloc

But the jemalloc dependency is not defined here: https://github.com/geerlingguy/ansible-role-ruby/blob/master/vars/Debian.yml#L9

[stale]

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[stale]

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