Valgrind is needed for testlib benchlibcallgrind selftest. Valgrind is
installed on Red Hat by default but needs to be separately installed on
Ubuntu and openSUSE.
Change-Id: I4cdfca512fe3efe9338a75cadc20454ff989fcae
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>
Reviewed-by: Heikki Halmet <heikki.halmet@qt.io>