This patch adds support to LLVM for writing HermitCore (https://hermitcore.org) ELF binaries.

HermitCore is a POSIX-compatible kernel for running a single application in an isolated environment to get maximum performance and predictable runtime behavior. It can either be used bare-metal on hardware or a VM (Unikernel) or side by side to an existing Linux system (Multikernel).
Due to the latter feature, HermitCore binaries are marked with ELFOSABI_STANDALONE to let the Linux ELF loader distinguish them from regular Unix/Linux binaries and load them using the HermitCore "proxy" tool.

Patch by Colin Finck!

llvm-svn: 340675