[CentOS] Slightly OT: Building latest ImageMagick on CentOS 3

I grabbed the latest ImageMagick.src.rpm (version 6.3.6, I believe)
from imagemagic.org and verified that I can compile it by hand on
CentOS 3.  I then commented out all the BuildPrereq and BuildRequires
lines and verified that "rpmbuild -bc ImageMagick.spec" behaved
sensibly.

However, when I try to run "rpmbuild -bb ImageMagick.spec" I get a
failure not because of any compilation problems but because the
PerlMagick got installed relative to the real root directory rather
than relative to the temporary build root, so none of those files
could be found when the final packaging step was done.

Can anyone give me some quick instructions on how to get those files
to install in the correct relative location?  My spec file foo is a
few years rusty.