[clang-tidy] Fix the condition for building CTTestTidyModule

This is the correct intended condition; the problematic case where
we don't want to try to build the plugin is "WIN32 AND LLVM_LINK_LLVM_DYLIB"
and thus the negation is "NOT WIN32 OR NOT LLVM_LINK_LLVM_DYLIB".

Differential Revision: https://reviews.llvm.org/D121687