VOL-5155 - triage failure in periodic-voltha-test-bbsim-2.12

.gitignore
----------
  o Ignore a.out and archives/ created late by the test target.

config.mk
makefiles/targets/sterile.mk
makefiles/targets/tox.mk
----------------------------
  o Update sterile target to remove the archives directory.
  o tox.mk updated to remove generated .tox/ directory.

jjb/pipeline/voltha/master/bbsim-tests.groovy
jjb/pipeline/voltha/voltha-2.12/bbsim-tests.groovy
--------------------------------------------------
  o Fixed a typo in the 'Combine and compress' banner.
  o In compress combined log block:
    - Display logs to compress.
    - '|| true' removed from gzip.  Wrap call with log collection
      and only invoke when logs are available (allow cmds to fail on err).

Change-Id: I141c0bbd1e8c946c652f00f21401bd897d8a4135
diff --git a/.gitignore b/.gitignore
index 0dc27e0..3ace541 100644
--- a/.gitignore
+++ b/.gitignore
@@ -42,4 +42,8 @@
 # Generated pipeline jobs
 build/
 
+# make test residue
+a.out
+archives/
+
 # [EOF]