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

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.

Differential Revision: https://reviews.llvm.org/D112776

Author: preames

llvm/docs/HowToAddABuilder.rst

@@ -121,6 +121,14 @@ Here are the steps you can follow to do so:
    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``.