get_mbed_official_release respects supported_toolchains

Author: bridadan

tools/build_api.py

@@ -364,13 +364,16 @@ def transform_release_toolchains(target, version):
               RELEASE_VERSIONS
     """
     if int(target.build_tools_metadata["version"]) > 0:
-        if version == '5':
-            if 'ARMC5' in target.supported_toolchains:
-                return ['ARMC5', 'GCC_ARM', 'IAR']
-            else:
-                return ['ARM', 'ARMC6', 'GCC_ARM', 'IAR']
-        else:
-            return target.supported_toolchains
+        if version == '5' and 'ARM' in target.supported_toolchains:
+            non_arm_toolchains = set(["IAR", "GCC_ARM"])
+            result = ["ARMC5", "ARMC6"]
+            result.extend(
+                set(target.supported_toolchains).intersection(
+                    non_arm_toolchains
+                )
+            )
+            return result
+        return target.supported_toolchains
     else:
         if version == '5':
             return ['ARM', 'GCC_ARM', 'IAR']