build_helper_configs: Set MCUboot dummy keys for stm32u5xxx

Add a workaround to set MCUboot dummy keys as default signing keys via
command line on b_u585i_iot02a platform.

Signed-off-by: David Hu <david.hu@arm.com>
Change-Id: I208255d7fb1c96a5966fa0d2789f44f5e59d72c0
diff --git a/build_helper/build_helper_config_maps.py b/build_helper/build_helper_config_maps.py
index 3f18400..5f53d33 100644
--- a/build_helper/build_helper_config_maps.py
+++ b/build_helper/build_helper_config_maps.py
@@ -114,5 +114,9 @@
     "EXAMPLE_DMA350_CLCD"     : ("-DDEFAULT_NS_SCATTER=OFF -DPLATFORM_SVC_HANDLERS=ON "
                                 "-DNS_EVALUATION_APP_PATH=%(codebase_root_dir)s/../tf-m-extras/examples/corstone310_fvp_dma/clcd_example "),
     "EXAMPLE_DMA350_S"        : "-DEXTRA_S_TEST_SUITE_PATH=%(codebase_root_dir)s/../tf-m-extras/examples/corstone310_fvp_dma/dma350_s",
-    "EXAMPLE_DMA350_NS"       : "-DEXTRA_NS_TEST_SUITE_PATH=%(codebase_root_dir)s/../tf-m-extras/examples/corstone310_fvp_dma/dma350_ns"
+    "EXAMPLE_DMA350_NS"       : "-DEXTRA_NS_TEST_SUITE_PATH=%(codebase_root_dir)s/../tf-m-extras/examples/corstone310_fvp_dma/dma350_ns",
+
+    # Set dummy MCUboot keys as default signing keys via command line
+    "DUMMY_MCUBOOT_KEY"       : ("-DMCUBOOT_KEY_S=%(codebase_root_dir)s/bl2/ext/mcuboot/root-RSA-3072.pem "
+                                 "-DMCUBOOT_KEY_NS=%(codebase_root_dir)s/bl2/ext/mcuboot/root-RSA-3072_1.pem ")
 }