Using LLVMTestingSupport in the LLVM_LINK_COMPONENTS breaks the build when
LLVM_TARGETS_TO_BUILD is set to empty.
Libraries that depend on LLVMTestingSupport need to use
target_link_libraries(<target> PRIVATE LLVMTestingSupport) instead.
This required change was already commited by r341899 to fix another build
issue.
This fixes rdar://problem/44615064.
llvm-svn: 342593