Disable Armclang as it's not supported yet

Signed-off-by: Kevin Peng <kevin.peng@arm.com>
Change-Id: I68abcd3da44e3679b636068b31d6c5bc4ae8ee01
diff --git a/build_helper/build_helper_configs.py b/build_helper/build_helper_configs.py
index 5ae9174..776b4a7 100755
--- a/build_helper/build_helper_configs.py
+++ b/build_helper/build_helper_configs.py
@@ -192,6 +192,8 @@
     ("arm/mps2/an519", "*", "3", "*", "*", "*", "*", "*", "*"),
     ("arm/mps3/an524", "*", "3", "*", "*", "*", "*", "*", "*"),
     ("arm/musca_s1", "*", "3", "*", "*", "*", "*", "*", "*"),
+    # Armlcang is not supported yet
+    ("*", "ARMCLANG_6_13", "*", "*", "*", "*", "*", "*", "*"),
     ]
 
 # Configure build manager to build several combinations