[cmake] Prevent linker errors by linking libswiftAST into SwiftBasicTests since libswiftBasic can include contents from libswiftAST.

I hit this in #72476. I put the declaration
that hit this in a header, but as I thought about it... there was no real harm
in just fixing the issue and preventing future breakage.

Author: gottesmm

unittests/Basic/CMakeLists.txt

@@ -48,6 +48,10 @@ add_dependencies(SwiftBasicTests "${gyb_dependency_targets}")
 target_link_libraries(SwiftBasicTests
   PRIVATE
   swiftBasic
+  # SwiftBasic can include symbols from swiftAST due to swiftBasic including
+  # headers from AST. Just include SwiftAST so that we do not have linker
+  # failures.
+  swiftAST
   swiftThreading
   clangBasic
   LLVMTestingSupport