Recommit "[libc++] NFC: Simplify substitutions by using lit recursive substitutions"
This re-commits cd7f9751c300, which was reverted in 12f6b024f9f5 because
it broke the LLVM check-all target. This commit addresses the underlying
issue by not setting the lit_config.recursiveExpansionLimit parameter of
the libc++ test suite, which is otherwise picked up by other test suites
Once we've settled on a fix for the underlying issue with
lit_config.recursiveExpansionLimit, we can start using it
again in libc++, but for now we can just work around it.