build_helper_configs.py: Switch config_debug to GNUARM

GNUARM is more mature, more well-known toolchain which is easier to
install for local testing.

Signed-off-by: Paul Sokolovsky <paul.sokolovsky@linaro.org>
Change-Id: I54e885003b554707dcb2c6f727552f7e6e9b6794
diff --git a/build_helper/build_helper_configs.py b/build_helper/build_helper_configs.py
index 603a40c..29640a1 100755
--- a/build_helper/build_helper_configs.py
+++ b/build_helper/build_helper_configs.py
@@ -1252,7 +1252,7 @@
 # Configuration used in testing
 config_debug = {"seed_params": {
                 "tfm_platform":     ["arm/mps2/an521"],
-                "toolchain_file":   ["toolchain_ARMCLANG.cmake"],
+                "toolchain_file":   ["toolchain_GNUARM.cmake"],
                 "lib_model":        [True],
                 "isolation_level":  ["1"],
                 "test_regression":  [False],