valgrind: look up tools from libexec dirs too

Current Fedora development has them in /usr/libexec/valgrind.

completions/valgrind

@@ -32,7 +32,7 @@ _valgrind()
             # Tools seem to be named e.g. like memcheck-amd64-linux from which
             # we want to grab memcheck.
             COMPREPLY=( $(compgen -W '$(
-                for f in /usr{,/local}/lib{,64}/valgrind/*; do
+                for f in /usr{,/local}/lib{,64,exec}/valgrind/*; do
                     [[ $f != *.so && -x $f ]] &&
                         command sed -ne "s/^.*\/\(.*\)-\([^-]*\)-\([^-]*\)/\1/p" <<<$f
                 done)' -- "$cur") )