torture: Make kvm-find-errors.sh find build warnings

Currently, kvm-find-errors.sh looks only for build errors ("error:"),
so this commit makes it also locate build warnings ("warning:").
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Nicholas Piggin <npiggin@gmail.com>

tools/testing/selftests/rcutorture/bin/kvm-find-errors.sh

@@ -22,9 +22,10 @@ editor=${EDITOR-vi}
 files=
 for i in ${rundir}/*/Make.out
 do
-	if grep -q "error:" < $i
+	if egrep -q "error:|warning:" < $i
 	then
-		files="$files $i"
+		egrep "error:|warning:" < $i > $i.diags
+		files="$files $i.diags $i"
 	fi
 done
 if test -n "$files"