The libnih test suite runs fine with or without dev-util/valgrind, but through test? ( dev-util/valgrind ) the test phase is blocked on platforms where valgrind isn't available.
In fact, configure checks for a valgrind header file and it is included in test_signal and test_child, but valgrind is never used directly.
sounds good http://gitweb.gentoo.org/repo/gentoo.git/commit/?id=72e04d1a06587ea8930af41209949852feaf5f39