This argument controls the compression requirements of different archive
formats and has the following values:
* 0-3 are fast levels with medium compression
* 4-6 are fairly slower with high compression
* 7-9 achieve higher compressions but require more memory
The default compression-level value in apache-commons-compress is 6.
This value consumes a large amount of heap memory, especially in Gerrit
tests, and causes UploadArchiveIT#verifyUploadArchiveFormats to fail
with "out of memory error": Java heap space. Having this option would
allow us to control the compression level value in tests to reduce the
memory footprint.
Change-Id: I3f87f322e172c9c1c0aeb596e036879efe9ba0a5
d507930c32