3a0f88c4c2
Some clients use libc++ with modules and LSV (Local Submodule Visibility) enabled, and we see frequent downstream breakage caused by that. Until modules use LSV by default (which is apparently a desire), add a CI job that tests this sub-configuration to avoid high cost downstream breakage. For more information about LSV, see https://lists.llvm.org/pipermail/cfe-commits/Week-of-Mon-20150504/128395.html. Differential Revision: https://reviews.llvm.org/D143273