TEMP_FAILURE_RETRY-like functionality in the support library (?)

Hello all,

I have a lldb patch under review in D33831, which adds the ability to
retry syscalls failing with EINTR (just a glorified
while(errno!=EINTR) loop, basically). It has been suggested that this
might be a useful utility function for llvm in general.

Looking at the code, there are a couple of places which could use this
utility function, although there is way fewer of them than in lldb.

So, what do you think? Would something like this be useful in the llvm
support library (perhaps in llvm/Support/Errno.h)? Is anyone opposed
to that?