[scheduler] Add convenience Makefile for common tasks.
[scheduler] Add convenience Makefile for common tasks.

R=hinoka@chromium.org, 9f116ddb1b24f6fc1916a676eb17161b6c07dfc1@chromium.org

Change-Id: I8e046a3cc6cc33e621e1f7313277884369468b0e
Reviewed-on: https://chromium-review.googlesource.com/1091654
Reviewed-by: Vadim Shtayura <9f116ddb1b24f6fc1916a676eb17161b6c07dfc1@chromium.org>
Commit-Queue: Andrii Shyshkalov <a30c74fa30536fe7ea81ed6dec202e35e149e1fd@chromium.org>

luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go