python: Ignore -s as gem5 option

This enables more compatibility with the normal python binary. This is
needed to get multiprocessing to work on some systems.

Change-Id: Ibb946136d153979bf54a773060010a0ae479a9d1
Signed-off-by: Jason Lowe-Power <jason@lowepower.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/71502
Maintainer: Bobby Bruce <bbruce@ucdavis.edu>
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Bobby Bruce <bbruce@ucdavis.edu>

src/python/m5/main.py

@@ -193,6 +193,13 @@ def parse_options():
         callback=collect_args,
     )
 
+    option(
+        "-s",
+        action="store_true",
+        help="IGNORED, only for compatibility with python. don't"
+        "add user site directory to sys.path; also PYTHONNOUSERSITE",
+    )
+
     # Statistics options
     group("Statistics Options")
     option(