[Differential] [Request, 8 lines] D3287: Make sure we don't break compilation with past broken units

[apol (Aleix Pol Gonzalez)]

apol created this revision.
apol added reviewers: Frameworks, dfaure.

REVISION SUMMARY
  Show a warning together with the old broken behavior

BRANCH
  master

REVISION DETAIL
  https://phabricator.kde.org/D3287

AFFECTED FILES
  KF5ConfigMacros.cmake

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To: apol, #frameworks, dfaure