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The target in the ``TARGET`` signature of :command:`add_custom_command`
must exist and must be defined in current directory.
CMake 2.8.12 and lower silently ignored a custom command created with
the ``TARGET`` signature of :command:`add_custom_command`
if the target is unknown or was defined outside the current directory.
The ``OLD`` behavior for this policy is to ignore custom commands
for unknown targets. The ``NEW`` behavior for this policy is to report
an error if the target referenced in :command:`add_custom_command` is
unknown or was defined outside the current directory.
This policy was introduced in CMake version 3.0. CMake version
|release| warns when the policy is not set and uses ``OLD`` behavior.
Use the :command:`cmake_policy` command to set it to ``OLD`` or
``NEW`` explicitly.
.. include:: DEPRECATED.txt
|