Using "make ps" at the top level with GDB does not work: make: *** No rule to make target `ps'. Stop. Postscript documents can be built by changing to the "doc" directory and using "make ps" there. However any images included (as EPS files) are not then found - they must be manually copied from the source "doc" directory to the build "doc" directory (this is an issue only for the recent update to gdbint.texinfo, which now includes a diagram). Note that on more recent Linuxes, building DVI, on which PostScript output depends may fail as described in Bug 9975. Problem demonstrated on Fedora Core 9 Linux and Centos 4.7 Linux.
Probably the top level won't ever support "make ps".