I havea minor suggestion for http://llvm.org/docs/TestingGuide.html:
Under 'Requirements', might be worth mentioning that running the basic llvm/clang regression tests (check-all) requires a version of bash that supports pipefail, i.e. bash 3.0+. On older system where /bin/sh is too old, one simply needs to hack LitConfig.py to point to /somewhere/else/bash that meets this requirement.
(This method has been tested on powerpc-darwin8.)