[CI] Add a runOnDiff flag to the build configurations

Summary:
This will allow for abcbot to retrieve which build should run when a
diff is updated. The selected set of builds is the current one +
build-clang-tidy.

Test Plan: Check the list builds that run on diff is as expected.

Reviewers: #bitcoin_abc, jasonbcox

Reviewed By: #bitcoin_abc, jasonbcox

Differential Revision: https://reviews.bitcoinabc.org/D6833