This page i am trying to cover what ever i have found during my setup and issue.

EXTRA_ECONF="--with-apxs=/home/apache/bin/apxs" emerge -O mod_security

Right now, users can replace the defaults:

 prefix, host, mandir, infodir, datadir, sysconfdir, localstatedir and
 datadir, infodir, localstatedir, mandir, sysconfir

add:

 anything that doesn't collide with additional arguments in the ebuild.

emerge -pv apg

emerge --sync