BL2: Add BL2 test code

Change-Id: I96f781b5de80e4a20121c596b1790259e98173f3
Signed-off-by: Raef Coles <raef.coles@arm.com>
diff --git a/bl2/ext/mcuboot/mcuboot_default_config.cmake b/bl2/ext/mcuboot/mcuboot_default_config.cmake
index 593971a..d23209a 100644
--- a/bl2/ext/mcuboot/mcuboot_default_config.cmake
+++ b/bl2/ext/mcuboot/mcuboot_default_config.cmake
@@ -1,5 +1,5 @@
 #-------------------------------------------------------------------------------
-# Copyright (c) 2021, Arm Limited. All rights reserved.
+# Copyright (c) 2021-2022, Arm Limited. All rights reserved.
 #
 # SPDX-License-Identifier: BSD-3-Clause
 #
@@ -7,6 +7,8 @@
 
 ########################## MCUBoot #############################################
 
+set(TEST_BL2                            OFF         CACHE BOOL      "Whether to build bl2 tests")
+
 set(DEFAULT_MCUBOOT_SECURITY_COUNTERS   ON          CACHE BOOL      "Whether to use the default security counter configuration defined by TF-M project")
 set(DEFAULT_MCUBOOT_FLASH_MAP           ON          CACHE BOOL      "Whether to use the default flash map defined by TF-M project")