Resurrect pselect MainLoop implementation
Summary:
It turns out that even though ppoll is available on all the android
devices we support, it does not seem to be working properly on all of
them -- MainLoop just does a busy loop with ppoll returning EINTR and
not making any progress.
This brings back the pselect implementation and makes it available on
android. I could not do any cmake checks for this as the ppoll symbol is
actually avaiable -- it just does not work.
Reviewers: beanz, eugene
Subscribers: srhines, lldb-commits
Differential Revision: https://reviews.llvm.org/D32600
llvm-svn: 301636