Fix shared library build after r291938 by adding missing dependency on libOption

Thanks to Reid Kleckner for the help reproducing/fixing.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@291953 91177308-0d34-0410-b5e6-96231b3b80d8

unittests/Driver/CMakeLists.txt

 set(LLVM_LINK_COMPONENTS
   Support
+  Option
   )
 
 add_clang_unittest(ClangDriverTests