[llvm] ErrorHandling: Check for EINTR and partial writes (PR #147595)

[Matthias Braun via llvm-commits]

MatzeB wrote:

I did not see any actual cases where things failed. (I was debugging build problems where no error message was given, but by now it looks like it's not LLVMs fault but the surrounding build system loosing the messages).

Anyway it seemed like the right thing to add this fix to LLVM if nothing else it will stop the next person wondering whether maybe an out-of-memory error message could be lost...

https://github.com/llvm/llvm-project/pull/147595