Add compiled python files to .gitignore.

Change-Id: If5d88d88bd1ea8189cc715cc38e70bd3b11c4b67
Reviewed-on: https://boringssl-review.googlesource.com/c/34950
Commit-Queue: Steven Valdez <svaldez@google.com>
Commit-Queue: David Benjamin <davidben@google.com>
Reviewed-by: David Benjamin <davidben@google.com>

.gitignore

@@ -1,5 +1,6 @@
 build/
 ssl/test/runner/runner
+*.pyc
 *.swp
 *.swo
 doc/*.html