rauthy: build against rust-jemalloc-sys-unprefixed
Required to fix rauthy on ARM systems with a 16 KiB page size.
rauthy uses unprefixed jemalloc:
https://github.com/sebadob/rauthy/blob/v0.34.3/Cargo.toml#L132
Signed-off-by: David Wronek <david.wronek@mainlining.org>
