Make sai library shared library, add install directives

[luspi]

Hi,

Thanks for providing this library!

I'm working on adding libsai support to my application, and for that needed to adjust the install process to also build a shared library and to install the files into the respective locations. This adds to CMakeLists.txt the SHARED keyword to the add_library command and provides install directives for the executables, the header file, and the library itself.

[Wunkolo]

Oh gosh sorry I managed to miss this for all this time, I'll get this merged soon!

[Wunkolo]

This looks good for a re-usable library, though I don't think this should be the default behavior and should instead be a CMake option of some kind. The Thumbnail, Decrypt, Tree, and Document are more like unit-tests and were never intended to be shipped user-facing binaries either 💦.

Does the library need to be shared in particular? I'd feel better about it just having to install a static library file(libsai.a) and the header file.

[BLumia]

I'm obviously not the author of libsai but just a random user, but why not make use of the CMake BUILD_SHARED_LIBS option? Hardcode it as a shared library is probably not the best option I guess?

In general we can put something like this in the CMakeLists.txt file, and make it defaults to ON if we want shared libs by default or OFF if otherwise:

option(BUILD_SHARED_LIBS "Prefer to build shared lib" ON)

And for installation, it could be better if we could reuse GNUInstallDirs too.

[luspi]

Thanks for the comments. I added a new commit to this pull request that:

• uses a BUILD_SHARED_LIBS option to toggle a shared build (off by default to match the current state of the code)
• uses include(GNUInstallDirs) to install the targets (I wasn't aware of GNUInstallDirs before, I'll use it in my own projects from now on too; thanks!)
• removes the installation of the binaries (since they, as you said, only really serve as unit tests)

[Wunkolo]

Looks good to me! Thank you both for your insight and contribution 🙏