Let me give you an example first... Take lirc for instance. To compile it you need to compile it like such..
LIRC_OPTS='--with-x --enable-debug --with-driver=hauppauge --with-major=61 --with-port=none --with-irq=none' emerge lirc
a bit long for a command line flag... what happens if you accidently emerge without all that (as I have done) and it's a headless box with just a remote control.. Well it doesn't work anymore.. I need to ssh in and correct it.
Users and Devs have long come up with alternate places to put this stuff. One example is /etc/make.conf, another is /etc/env.d/, yet another I've seen is .bashrc.
None of that makes sense... what I propose is to add a file, /etc/portage/env.opts
where users can specify these FLAGS. There a several other packages that exist like this. This also will allow other overrides in packages which aren't as well noted.
Steps to Reproduce:
*** This bug has been marked as a duplicate of 44796 ***