Improve FindSphinx.cmake when installed with MacPorts
Improve FindSphinx.cmake when installed with MacPorts

In this case, the name of the executable is sphinx-build-${version} where
${version} is the python version number

InsightSoftwareConsortium/ITKExamples,InsightSoftwareConsortium/ITKExamples,InsightSoftwareConsortium/ITKExamples,InsightSoftwareConsortium/ITKExamples,InsightSoftwareConsortium/ITKExamples