CMake: Honor standard variables

[nbraud]

• Do not ignore the variables that control CMake's RPATH handling,
  such as CMAKE_INSTALL_RPATH (which is enabled by default anyway)
• Honor the standard CMAKE_INSTALL_* variables for install directories.

Both of those changes came up when packaging v2.1.1 for Debian,
as the CMake-based build system was failing to obey any of the standard
configuration variables.

This change should be backwards compatible, in that the defaults should
stay the same, and users who previously set YKPIV_* still override any
other variables.

[nbraud]

6a91dcd got merged, then immediately reverted by 283e2e7.
Could you explain why / what happened?

[aveenismail]

Hi @nbraud

It was necessary to specifically set the RPATH when building for MacOS, otherwise the library and the commandline tool weren't linking correctly. We didn't see that setting the RPATH made a difference when building for a Linux system, and that's why we left it there.

Did you see a different behavior with Debian? Do you see a downside for doing it this way?

[nbraud]

Did you see a different behavior with Debian? Do you see a downside for doing it this way?

Yes, this makes the build non-reproducible, i.e. rebuilding the same source, with the same toolchain, will give different results depending on the build path. Setting CMAKE_BUILD_RPATH_USE_ORIGIN or CMAKE_BUILD_WITH_INSTALL_RPATH might work to have builds that are both reproducible-by-default and work on macOS.

[aveenismail]

An update was committed to set INSTALL_RPATH only when building on MacOS. I hope this resolves the issue