I had to uninstall RH7 in favor of RH6.2 because the new gcc and glibc packages make it impossible to compile packages which previously had no issues (rxvt is a good example). I don't have a configure/make log, because I reinstalled over it. Renaming /usr/bin/gcc to gcc-2.96 and symlinking /usr/bin/gcc to /usr/bin/kgcc helped some, but it still caused linker errors against the new libc. I guess I'm just having trouble undertanding the reasoning behind shipping prerelease versions of these products with RH7 when perfectly good, compatible versions are available. Furthermore, there is no mention anywhere except the kgcc spec that kgcc should be used to build kernels - and building from stock source (rather than yours which has been patched to use kgcc) is an excercise in unbelievable frustration. As one of the first RHCEs, I was quite impressed with your products in the past, obviously. But I'm starting to reconsider, based on these questionable choices.
The new gcc and glibc are stricter and more standards compliant. Maybe rxvt is the problem. How about attaching a build log I agree btw about the lack of documentation on kgcc.
I agree there should perhaps be a man page for kgcc, but at least it is mentioned in the release notes that you should use kgcc to build kernels. Use make CC='kgcc -D__KERNEL__ -I$(HPATH)' to compile stock kernels unless you compile 2.2.18pre which already have that logic in (for 2.4 you can build either with normal gcc, or if you want to play safe, make CC=kgcc (note no longer -D and -I)). As for rxvt, without a build log I cannot tell much, perhaps if you tell me URL where you grabbed sources and which version was it, I can reproduce it and let you know details.
I've tried to build ftp://ftp.rxvt.org/pub/rxvt/rxvt-2.7.5.tar.gz which seems is the latest and it compiled out of the box on a fresh RHL7, so I'm really waiting for any details, because otherwise there is nothing I can do about it. Please reopen the bug if you have anything I can work on.