comms/rxtx: Set MAKE_JOBS_UNSAFE

[leres]

Summary

Please double check me on the Approved by, koobs@ set the maintainer
approval flag but [e-mail] has recently started chiming in.

Here's the PR link for convenience:

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=216558

Proposed commit message:

Solve occasional poudriere build failures by adding MAKE_JOBS_UNSAFE.

PR:		216558
Submitted by:	
Reported by:	
Reviewed by:	? (mentor)
Approved by:	koobs (maintainer), ? (mentor)
Obtained from:	
MFC after:	
MFH:		
Relnotes:	
Security:	
Sponsored by:	
Differential Revision:	?

[matthew]

LGTM

Good to commit so long as you have maintainer approval too.

[mat]

Why bump PORTREVISION?

[leres]

Don't bump PORTREVISION as per mat@

[mat]

Also, please include in the commit message a few lines of the build log showing the build error without MAKE_JOBS_UNSAFE.