Sink add_llvm_library(gtest_main) to UnitTestMain/CMakeLists.txt.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@198933 91177308-0d34-0410-b5e6-96231b3b80d8
Whitespace.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@198934 91177308-0d34-0410-b5e6-96231b3b80d8