[ELF] Return error from invalid linker script parse.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@192360 91177308-0d34-0410-b5e6-96231b3b80d8
[test] Ignore failure for now for Darwin.

This is only a step to clean the buildbot.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@192368 91177308-0d34-0410-b5e6-96231b3b80d8
[ELF] Initial design to handle Linker scripts for ELF.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@192369 91177308-0d34-0410-b5e6-96231b3b80d8