fix(libextism): improve static linking pkgconfig

[G4Vi]

This includes two fixes:

• link static library by absolute path (should fix static linking on Mac/ with lld)
• link libpthread , this should be a no-op on systems with modern libc, but should fix static linking on systems with glibc pre 2.34 see https://developers.redhat.com/articles/2021/12/17/why-glibc-234-removed-libpthread and error http://www.cpantesters.org/cpan/report/669fdfc8-25a4-11ef-9502-51fb6d8775ea

@zshipko if you could verify make pkg-config-static and the resulting example executable in libextism works on Mac that would be greatly appreciated.

[zshipko]

I just pushed a commit to fix the libextism example on macOS - the only thing I didn't fix is on macOS -framework Security also needs to be linked in the static pkg-config file - what do you think the best way of handling that is?

[G4Vi]

Thanks! The best way of handling it is probably adding another variable to the template, extism-static-pc.in, and having the cli fill it in like it does for the prefix. Normally it would be empty, but on mac it would have -framework Security

[zshipko]

Alright I can add that - I think I can probably do something similar but avoid adding a variable so we maintain compatibility with existing CLI installations

[G4Vi]

Maintaining compatibility is better, good idea.

[zshipko]

Alright, this seems to be working now - let me know if you see anything that looks off @G4Vi (I don't think you can "review" your own PR)

I also have extism/cli#94 ready to merge

[G4Vi]

Looks good to me. The only thing I wonder about is -framework Security being part of Libs instead of Libs.private, but if it needs to go before libextism when it has to. Have you seen any other pkgconfig that uses it?

If you review I can merge without bypassing branch protections.

[zshipko]

Including it in Libs.private still resulted in the linker error but Libs worked - I'm not sure why though. It could be the order of the libraries, but based on this search https://github.com/search?q=%22-framework+Security%22+path%3A*.pc&type=code it looks like people are using both Libs and Libs.private.