rcutorture: Add --buildonly dry-run capability

This commit adds --buildonly, which does the builds specified by the
--configs argument, but does not boot or test the resulting kernels.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Greg KH <gregkh@linuxfoundation.org>

tools/testing/selftests/rcutorture/bin/kvm-test-1-rcu.sh

@@ -141,6 +141,11 @@ boot_args="`rcutorture_param_n_barrier_cbs "$boot_args"`"
 boot_args="$boot_args rcutorture.stat_interval=15 rcutorture.shutdown_secs=$seconds rcutorture.rcutorture_runnable=1"
 
 echo $QEMU $qemu_args -m 512 -kernel $builddir/arch/x86/boot/bzImage -append \"$qemu_append $boot_args\" > $resdir/qemu-cmd
+if test -n "$RCU_BUILDONLY"
+then
+	echo Build-only run specified, boot/test omitted.
+	exit 0
+fi
 $QEMU $qemu_args -m 512 -kernel $builddir/arch/x86/boot/bzImage -append "$qemu_append $boot_args" &
 qemu_pid=$!
 commandcompleted=0

tools/testing/selftests/rcutorture/bin/kvm.sh

@@ -41,6 +41,7 @@ kversion=""
 usage () {
 	echo "Usage: $scriptname optional arguments:"
 	echo "       --builddir absolute-pathname"
+	echo "       --buildonly"
 	echo "       --configs \"config-file list\""
 	echo "       --datestamp string"
 	echo "       --duration minutes"
@@ -83,6 +84,9 @@ do
 		gotbuilddir=1
 		shift
 		;;
+	--buildonly)
+		RCU_BUILDONLY=1; export RCU_BUILDONLY
+		;;
 	--configs)
 		checkarg --configs "(list of config files)" "$#" "$2" '^[^/]*$' '^--'
 		configs="$2"