CMAKE_INCLUDE_DIRECTORIES_BEFORE
Whether to append or prepend directories by default in include_directories().
This variable affects the default behavior of the include_directories() command. Setting this variable to ON is equivalent to using the BEFORE option in all uses of that command.
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Licensed under the BSD 3-clause License.
https://cmake.org/cmake/help/v3.6/variable/CMAKE_INCLUDE_DIRECTORIES_BEFORE.html
