tests: Fix verifier to ignore downloader stdout

This part of the fix for the following nightly build error:
https://www.mail-archive.com/gem5-dev@gem5.org/msg40426.html.

The new resource downloader outputs messages to stdout informing the
user of the download status. For tests which compare the stdout to some
reference, these lines need ignored.

Change-Id: Ic209c37a6511f8eebf5a940dd01c769d0eb971fc
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/50227
Reviewed-by: Bobby R. Bruce <bbruce@ucdavis.edu>
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Maintainer: Bobby R. Bruce <bbruce@ucdavis.edu>
Tested-by: kokoro <noreply+kokoro@google.com>

tests/gem5/verifier.py

@@ -154,6 +154,8 @@ class MatchStdout(DerivedGoldStandard):
             re.compile("^info: Standard input is not a terminal"),
             re.compile("^Couldn't unlink "),
             re.compile("^Using GPU kernel code file\(s\) "),
+            re.compile("^.* not found locally\. Downloading"),
+            re.compile("^Finished downloading"),
         ]
 
 class MatchStdoutNoPerf(MatchStdout):