[ELF] Use std::find_if instead

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@221426 91177308-0d34-0410-b5e6-96231b3b80d8
[ELF] Implement isLittleEndian for all architectures

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@221427 91177308-0d34-0410-b5e6-96231b3b80d8
[ELF] Use llvm::Twine

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@221428 91177308-0d34-0410-b5e6-96231b3b80d8