Link liblldb.so with LLVMObjCARCOpts.a

Summary:
Problems reported on NetBSD:

```
llvm[4]: Linking Debug+Asserts executable lldb
/tmp/build-llvm/Debug+Asserts/lib/liblldb.so: undefined reference to `llvm::createObjCARCExpandPass()'
/tmp/build-llvm/Debug+Asserts/lib/liblldb.so: undefined reference to `llvm::createObjCARCOptPass()'
/tmp/build-llvm/Debug+Asserts/lib/liblldb.so: undefined reference to `llvm::createObjCARCAPElimPass()'
/tmp/build-llvm/Debug+Asserts/lib/liblldb.so: undefined reference to `llvm::createObjCARCContractPass()'
clang: error: linker command failed with exit code 1 (use -v to see invocation)
 /tmp/llvm/Makefile.rules:1434: recipe for target '/tmp/build-llvm/Debug+Asserts/bin/lldb' failed
```

Reviewers: joerg, sas

Subscribers: brucem, sas, lldb-commits

Change by Kamil Rytarowski <n54@gmx.com>

Differential Revision: http://reviews.llvm.org/D12749

llvm-svn: 247383