Build: corstone1000: Edit the flash.bin creation cmd

Concatinating the binaries will not work with the new corstone1000
GPT image. Instead of cat command, a custom script should be called to
create the flash image.

Signed-off-by: Mohamed Omar Asaker <mohamed.omarasaker@arm.com>
Change-Id: Ib15b2496db231ce497c2a1381120ee2a947942e6
diff --git a/build_helper/build_helper_configs.py b/build_helper/build_helper_configs.py
index 281463b..0059000 100755
--- a/build_helper/build_helper_configs.py
+++ b/build_helper/build_helper_configs.py
@@ -86,18 +86,7 @@
                                  "-fill 0xFF 0xA020000 0xA200000 "
                                  "-o %(_tbm_build_dir_)s/bin/"
                                  "tfm.hex -Intel")],
-                   "arm/corstone1000": [("cat "
-                                         "%(_tbm_build_dir_)s/bin/"
-                                         "bl2_signed.bin "
-                                         "%(_tbm_build_dir_)s/bin/"
-                                         "bl2_signed.bin "
-                                         "%(_tbm_build_dir_)s/bin/"
-                                         "tfm_s_signed.bin "
-                                         "%(_tbm_build_dir_)s/bin/"
-                                         "tfm_s_signed.bin "
-                                         "> "
-                                         "%(_tbm_build_dir_)s/bin/"
-                                         "flash.bin")],
+                   "arm/corstone1000": [("%(_tbm_build_dir_)s/../platform/ext/target/arm/corstone1000/create-flash-image.sh %(_tbm_build_dir_)s/bin flash.bin")],
                    "arm/musca_s1": [("srec_cat "
                                  "%(_tbm_build_dir_)s/bin/"
                                  "bl2.bin "