this module looks for gnuplot
Once done this will define
GNUPLOT_FOUND - system has Gnuplot GNUPLOT_EXECUTABLE - the Gnuplot executable GNUPLOT_VERSION_STRING - the version of Gnuplot found (since CMake 2.8.8)
GNUPLOT_VERSION_STRING will not work for old versions like 3.7.1.
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© 2000–2011 Insight Software Consortium
Licensed under the BSD 3-clause License.
https://cmake.org/cmake/help/v3.7/module/FindGnuplot.html