X Default to running tests live, not under QEMU

test.sh

 #!/bin/bash -e
-# run wendelin.core/wcfs tests under custom linux kernel
+# run wendelin.core/wcfs tests.
+# if $WENDELIN_CORE_TEST_QEMU_RUNLINUX=y the tests are run under custom linux kernel.
 
 X=$(cd `dirname $0` && pwd)
 
-if test -z "$qrun_loglevel"; then
-	make -C $X --no-print-directory # rebuild everything
-	linux=${LINUX:-$HOME/src/linux/linux/arch/`uname -m`/boot/bzImage}
-	exec $X/t/qemu-runlinux "$linux" $0 "$@"
+# respawn ourself under qemu-runlinux, if asked.
+if [ "${WENDELIN_CORE_TEST_QEMU_RUNLINUX:-n}" == y ]; then
+	if test -z "$qrun_loglevel"; then
+		make -C $X --no-print-directory # rebuild everything
+		linux=${LINUX:-$HOME/src/linux/linux/arch/`uname -m`/boot/bzImage}
+		exec $X/t/qemu-runlinux "$linux" $0 "$@"
+	fi
 fi
 
 # executed under qemu-runlinux