Creating an SRPM with customized build option

[Quentin Spencer <qspencer ieee org>]

Hi All,
I've packaged ATLAS, a speed-optimized linear algebra library (which by 
the way still needs a reviewer--see bug #166871). The package uses 
compile-time optimizations to achieve a lot of the speed gains, which 
creates output that is of course dependent on the hardware it was 
compiled on. In order to get around this problem, I've used the Debian 
patches, which use a "prerecorded build" scheme to replicate builds done 
on "average" hardware that will give reasonable performance on a range 
of hardware. For users who desire libraries that are truly optimized for 
their hardware, the Debian package provides a means of rebuilding the 
source package with the compile-time optimizations re-enabled. I'd like 
to provide such a function for the SRPM I'm creating. My current 
thinking is to use a macro definition to enable this so that a 
customized build can be triggered using something like:

rpmbuild -rebuild atlas-<version>.src.rpm -D _custom_atlas_build=1

My question is what makes the most sense to do with the resulting 
libraries? Should the customized build create an RPM by a different name 
such as atlas-custom rather than atlas so it's clear that it's different 
from the FE package? Should the libraries be put in a new location so 
that the RPM can be installed on a system with an existing atlas package 
installed? I was thinking along the lines of putting the libraries in a 
special path (/usr/lib/atlas-custom, for example) and putting a file in 
/etc/ld.so.conf.d/ that would make the customized libraries load 
automatically. I welcome any suggestions.

-Quentin