I've been seeing a problem with xcodebuilds on macosx for

a few days now where compiler-rt gets an error when trying
to run its install step (related to not being able to find
an ios version of a dylib), breaking the lldb build.  I
don't know if I'm the only one seeing this or if everyone has
been doing the same hack I've been doing - removing the
compiler-rt project from the default checkout.

It's only used for the ASAN test case.  So I'm temporarily
checking in my hackaround of not checking out compiler-rt
by default, I'll try to get back and look at what's actually
happening in the compiler-rt install step that is causing
the problems when built as a part of lldb.

llvm-svn: 250487