Install tree should be relocatable

[jcfr]

PR https://github.com/Slicer/vtkAddon/pull/6 improved the build-system to properly install artifacts

The configured vtkAddonInstallConfig.cmake.in should be improved so that it does NOT contain absolute paths:

https://github.com/Slicer/vtkAddon/blob/965cb2ed60be68c611501ff565396205a4dcd876/vtkAddonInstallConfig.cmake.in#L1-L4

The following resources may be helpful to learn how to move forward:

• https://stackoverflow.com/questions/51564251/correct-way-to-use-third-party-libraries-in-cmake-project/51567322#51567322

• https://stackoverflow.com/questions/56135785/correctly-set-the-location-of-imported-cmake-targets-for-an-installed-package/56288628#56288628

  • and associated demo project: https://github.com/jcfr/stackoverflow-56135785-answer

Some CMake projects:

• proxTV: https://github.com/phcerdan/proxTV/blob/a503293ed567d7114bee85e4e068305d4afe7dbe/CMakeLists.txt#L84-L136

• python-cmake-buildsystem: https://github.com/python-cmake-buildsystem/python-cmake-buildsystem/blob/2b036f110364a9295760345c9bbb3337c2ca9d72/CMakeLists.txt#L636-L687

• CTKAppLauncher: https://github.com/commontk/AppLauncher/blob/1c7156701ee96ab7b69ecc8322dc5443514927fa/CMakeLists.txt#L363-L469

[RafaelPalomar]

@jcfr, I'll have a look at this. Thanks for taking your time to make it that informative.

[jcfr]

Thanks for your help and thanks for contributing :pray: