My bad for not keeping the exchange with Dustin on the group... forgot to do a cc.
Anyway, the main problem is solved, with Dustin's help! Redux: astrometry.net-0.89 does NOT build on RHEL 7, or at least not on SL 7.9. I needed to clone the source code tree from github, and really nothing else other than maybe making sure /usr/include/netpbm was in the includes search path.
There is still one outstanding problem, namely that cairoutils.c and plotquad.c don't compile due to the compiler not being able to find cairo.h. This was NOT fixed by putting /usr/include/cairo in the includes search path, i.e.
%setenv CAIRO_INC "-I/usr/include/cairo"
from the C-shell prior to make.
I realise these utilities are "eye-candy", but I'd still like to have them. Any ideas? (The output of `make install` is attached.)