Description of problem: brp-compress runs gunzip without -f ; in some cases, this causes rpmbuild to hang, waiting for the user eg. gunzip: ./usr/share/info/R-intro.info already exists; do you wish to overwrite (y or n)? y Version-Release number of selected component (if applicable): 4.2-0.69
Yup, but there's no easy and reliable fix here except to remove precompressed manpages in the %install scriptlet, there's too many versions of brp-compress already released.
I'm not suggesting that there is a real fix, but I merely that it should fail with some error message, in stead of user interaction -- if user interaction is acceptable, then -f is, too, and for a batch program like rpmbuild, -f is more appropriate than a prompt.