Detect test skips with armc6

Author: theotherjimmy

tools/toolchains/arm.py

@@ -320,6 +320,9 @@ def __init__(self, target, *args, **kwargs):
     def parse_dependencies(self, dep_path):
         return mbedToolchain.parse_dependencies(self, dep_path)
 
+    def is_not_supported_error(self, output):
+        return "#error [NOT_SUPPORTED]" in output
+
     def parse_output(self, output):
         pass