[NANO130] rollback arm.py

Author: cyliangtw

tools/toolchains/arm.py

@@ -162,10 +162,6 @@ def compile(self, cc, source, object, includes):
 
         cmd.extend(self.get_dep_option(object))
 
-        # Remove '.\' from relative path names of source files. For example, '.\mbed-os\platform\retarget.cpp' will truncate to 'mbed-os\platform\retarget.cpp'.
-        if source.startswith('.\\'):
-            source = source[2:]
-
         cmd.extend(["-o", object, source])
 
         # Call cmdline hook