zephyr: CMakeLists.txt: support nrfjprog mass erase flag

The upstream Zephyr runner for nrfjprog now supports an --erase
toggle, which controls whether a mass-erase is done. Add that to its
invocation when CONF_ZEPHYR_TRY_MASS_ERASE is given, just like is done
for dfu-util and pyocd.

Signed-off-by: Marti Bolivar <marti@foundries.io>

boot/zephyr/CMakeLists.txt

@@ -53,6 +53,7 @@ macro(app_set_runner_args)
   if(CONFIG_ZEPHYR_TRY_MASS_ERASE)
     board_runner_args(dfu-util "--dfuse-modifiers=force:mass-erase")
     board_runner_args(pyocd "--flashtool-opt=-ce")
+    board_runner_args(nrfjprog "--erase")
   endif()
 endmacro()