Temporarily use procfs for rust ports
Temporarily use procfs for rust ports

On DragonFly (only), Rust needs procfs to operate and build.  This is
an undesirable situation, but it will take some time to rectify.  Thus,
when lang/rust and lang/rust-nightly are being built, procfs will be
mounted (even on FreeBSD).

Hopefully this can be removed later.

jrmarino/synth,jrmarino/synth,jrmarino/synth,jrmarino/synth