It's imported from test/interrupt.c and adjusted to CTS.
BUG=chromium:624520
BRANCH=none
TEST=make buildall. Test passed on stm32l476-geval and nucleo-f072rb.
Change-Id: Ie948d284cebad60d97aab1512bb9e3af8838004e
Signed-off-by: Daisuke Nojiri <dnojiri@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/360660
Reviewed-by: Chris Chen <twothreecc@google.com>
