[docs] Update new builder instructions to default to building each change

[reames]

Summary

We generally prefer build bots which build each change as they come in as long as they can keep up. This generates much higher quality feedback to a developer. However, the code structure is such that we currently default new builders to batching.

This change updates the getting started instruction for a builder to explicitly advocate for not collapsing requests.

[mehdi_amini]

llvm/docs/HowToAddABuilder.rst

130

This is a question for Galina I guess: is there a way to configure something like maxCollapse = 3 in buildbot instead of just letting some bots email 20 people at the same time?

[reames]

llvm/docs/HowToAddABuilder.rst

130

I don't believe there is currently, but this was one of the ideas I was thinking about implementing.

[gkistanova]

Thanks, Philip!

llvm/docs/HowToAddABuilder.rst

130

Out of the box there is no way to limit a number of collapsed build requests. It could be implemented, though.
I'm looking in to this.

llvm/docs/HowToAddABuilder.rst

#. Send a patch which adds your build worker and your builder to
    `workflow <https://llvm.org/docs/Contributing.html#how-to-submit-a-patch>`_.
 
    * workers are added to ``buildbot/osuosl/master/config/workers.py``
    * builders are added to ``buildbot/osuosl/master/config/builders.py``
 
    Please make sure your builder name and its builddir are unique through the
    file.
 
+   All new builders should default to using the "'collapseRequests': False"
+   configuration.  This causes the builder to build each commit individually
+   and not merge build requests.  To maximize quality of feedback to developers,
+   we *strongly prefer* builders to be configured not to collapse requests.
+   This flag should be removed only after all reasonable efforts have been
+   exhausted to improve build times such that the builder can keep up with
+   commit flow.
+
    It is possible to allow email addresses to unconditionally receive
    notifications on build failure; for this you'll need to add an
    ``InformativeMailNotifier`` to ``buildbot/osuosl/master/config/status.py``.
    This is particularly useful for the staging buildmaster which is silent
    otherwise.
 
 #. Send the buildbot-worker access name and the access password directly to
    `Galina Kistanova <mailto:[e-mail]>`_, and wait till she