Gentoo prefix tries to install to /usr/bin
 

I am trying to build dvd+rw-tools-7.1 in Gentoo prefix on Mac OS X (one of the dependencies of bombono-dvd). The build fails with

install: cannot create regular file ‘/usr/bin/growisofs’: Permission denied
....

Since the whole point of a prefix install is to do without root privileges, I have to ask if ambitious builds are possible at all, or if it is possible to modify the ebuilds to install everything in the prefix tree. Are there tools for modifying ebuilds?

Edit: I added an export EPREFIX=/opt/Gentoo to $EPREFIX/etc/bash/bashrc, but now i get an error message in /opt/Gentoo/var/tmp/portage/app-cdr/dvd+rw-tools-7.1/temp/build.log:

install: cannot create regular file <E2><80><98>/usr/bin/growisofs<E2><80><99>: Permission denied

What the fsck is going on?

Edit:
What does this mean?
emake SHELL=/bin/bash prefix="${D}/usr" install || die;

Where is ${D} defined? Google does not show up anything

It's possible, but don't expect every ebuild to compile on a prefix install. Gentoo has to deal with lots of different build scripts, some broken by design, and some that change from time to time. You might need to patch some packages. Don't forget to submit fixes to bugs.gentoo.org if you happen to produce any ;)

Regular users do not have write permissions on /opt (or in any other place for that matter, besides their $HOME, /tmp and little more). That's not Gentoo, it's how *nix has been for ages.

You can start here:

http://devmanual.gentoo.org/

You won't get much support for Gentoo development questions in here. I advise you to either go to the portage and programming subforum at the official gentoo forums, or to the gentoo dev channels in freenode, or the gentoo-dev mailing list for the specific purpose you are seeking. That'd be anything with "dev" on its name on this list:

http://www.gentoo.org/main/en/lists.xml

Solved - I managed to build bombono directly in Mac OS X, with dependencies mostly from Macports. I posted the results in the Other *NIX section. I'm afraid I'll give up on Gentoo Prefix; from what I've seen of it I don't like it at all.

Thank you, i92guboj. As for /opt/Gentoo, I have write permissions as a regular user. I'll take a look at the gentoo devmanual, and if I ever try gentoo again, I'll do it as a regular install.