CMake Warning at ON-byproduct\.cmake:[0-9]+ \(add_test\):
  Test "ByproductTest" BUILD_DEPENDS file

    .*/TestDependencyByproduct-built\.txt

  is generated but is not the unique output of a build target, so the
  "test_prep/ByproductTest" target cannot build it with this generator\.
  Depend on the target that produces it \(for example one created with
  add_custom_target\) instead\.
