dev-util/valgrind: fix as-needed breakage found by Diego
tree54612eece945ddae7aa8f0e041867f7f6b01272a
drwxr-xr-x - app-misc
drwxr-xr-x - dev-lang
drwxr-xr-x - dev-ml
drwxr-xr-x - dev-util
drwxr-xr-x - dev-vcs
drwxr-xr-x - games-arcade
drwxr-xr-x - media-sound
drwxr-xr-x - net-fs
drwxr-xr-x - net-libs
drwxr-xr-x - net-p2p
drwxr-xr-x - profiles