The proposed solution is in the tracker.
If this is an autotools based package, and '--disable-silent-rules' doesn't work, you can try:
- emake V=1 in src_compile() and/or src_install()
- MAKEOPTS+=" V=1" as global scope
Note: if you will port the ebuild to EAPI 5, it includes '--disable-silent-rules'
the non-verbose part is ftjam building itself, and that's as verbose as ftjam gets. :p