Unreliable buildbots

There's a thread discussing LLDB buildbot unreliability taking place
on llvm-commits. I just noticed that lldb-dev isn't on the CC. The
discussion started on the topic of the FreeBSD LLDB builder but
progressed to discussing the general unreliability across the bots.

http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20150511/275854.html

Should all of the LLDB bots (perhaps other than the Windows build-only
bots) be moved to the experimental category so that they don't
generate failure emails? Should we have (in addition) build-only
configurations for Darwin/FreeBSD/Linux?