As part of an ongoing effort to remove FreeBSD's reliance on the end-of-life COMPAT_FREEBSD11 option, all rust crates that have FreeBSD ports should be updated to libc>=0.2.151. See this commit[1] for more info.
[1] rust-lang/libc@f5172d2
Gluon master branch currently targets 0.2.167, which is good. Please tag a new release whenever possible to allow the FreeBSD port to take this change.