Allow cath-tools to build using libgsl.so in addition to libgsl.a

[anadon]

More Arch Linux related things, which typically cascade out to other distributions after a few years.

cath-tools requires a static library for GSL, but my systems only provide a .so. Given that this is likely to be the standard behavior for more distributions in the future, I'll be throwing another small merge request shortly.

I think I didn't catch this because I tested that part only on Ubuntu 17.10, and only checking the configuration on arch.

[anadon]

I'm looking into how to infer which type of library is supported, but it looks like it might require a manual switch. Can I get someone else's thoughts on this?

[tonyelewis]

I'm open to you issuing a PR to add some sort of manual switch to allow you to use shared in your case. But I want static to remain the default because I want the default build to create executables that work on a machine equivalent to the build machine but without GSL installed.

Perhaps you could use a suitably named environment variable (eg CATH_TOOLS_STATIC_LINK_GSL) and detect the presence of that in CMakeLists.txt?

[anadon]

OK. I'll get to adding that tomorrow. It will also need an addition in the documentation, which I don't think I can edit.

[tonyelewis]

Do you mean the documentation on Read the Docs? That's generated from the files in the docs subdirectory (eg https://github.com/UCLOrengoGroup/cath-tools/blob/736d31ce30ec97c5873e179b20226ddad788f829/docs/build.md)

[anadon]

I stand corrected.

[tonyelewis]

NP :smiley: