Fixed some exec test cases

mjtest/environment.py

@@ -155,7 +155,7 @@ class Environment:
             return dst_file
         self._already_preprocessed_files.add(dst_file)
 
-        if os.path.exists(dst_file) and os.path.isfile(dst_file) and os.path.getmtime(file) < os.path.getmtime(dst_file):
+        if os.path.exists(dst_file) and os.path.isfile(dst_file) and os.path.getmtime(file) < os.path.getmtime(dst_file) and False:
             _LOG.debug("File '{}' already exists in a pre processed form".format(os.path.relpath(file)))
             return dst_file
         cur = os.path.split(dst_file)[0]