Add linux_rel_alt to bot_update
Add linux_rel_alt to bot_update

This is an experimental builder living on the tryserver, we can use this
to test out patching for bot_update.

BUG=339171

Review URL: https://codereview.chromium.org/167773004

git-svn-id: 239fca9b83025a0b6f823aeeca02ba5be3d9fd76@251849 0039d316-1c4b-4281-b951-d872f2087c98

eunchong/build,eunchong/build,eunchong/build,eunchong/build