Building NetBSD system: what is PIGSGZIP?

["Thomas Mueller" <mueller6724%bellsouth.net@localhost>]

I look at the build.sh command line in the build logs on 
http://releng.netbsd.org/cgi-bin/builds.cgi

and at least for HEAD and netbsd-6, one parameter is
USE_PIGZGZIP=yes

What is this, and would it make a build succeed that would otherwise fail?

I just used the search on netbsd.org and found what it is, but how would it 
affect a system build?

I see /usr/bin/pigz is in NetBSD base system but not FreeBSD; however pigz is 
listed in archivers for both pkgsrc and FreeBSD ports.

Tom