For CMake 2.4 compatibility only. Use COMPILE_DEFINITIONS instead.
This read-only property specifies the list of flags given so far to the add_definitions() command. It is intended for debugging purposes. Use the COMPILE_DEFINITIONS directory property instead.
This built-in read-only property does not exist if policy CMP0059 is set to NEW.
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Licensed under the BSD 3-clause License.
https://cmake.org/cmake/help/v3.19/prop_dir/DEFINITIONS.html