gem5: update to bcf041f257623e5c9e77d35b7531bae59edc0423

This notably allow dynamic linking to work! Move entire README to it.

Also:

- explain what Dhrystone does and run it on gem5 to get DMIPS
- create getprops
- ./test-executables don't test files that start with "tmp."

getprops

@@ -0,0 +1,27 @@
+#!/usr/bin/env python3
+
+import common
+import json
+import path_properties
+
+class Main(common.LkmcCliFunction):
+    def __init__(self):
+        super().__init__(
+            defaults = {
+                'show_time': False,
+            },
+            description='''\
+Get the path_properties for an userland executable:
+https://cirosantilli.com/linux-kernel-module-cheat#path-properties
+TODO check that the path exists.
+''',
+        )
+        self.add_argument('path')
+
+    def timed_main(self):
+        properties = path_properties.get(self.env['path']).properties
+        for key in sorted(properties):
+            print('{}={}'.format(key, properties[key]))
+
+if __name__ == '__main__':
+    Main().cli()