upgrading c-api cmake

[scarrazza]

This fixes compilation and installation issues on linux and mac, however on mac I cannot run the example using python3 from Xcode:

dyld[15376]: Library not loaded: @rpath/Python3.framework/Versions/3.9/Python3
  Reason: no LC_RPATH's found
Abort trap: 6

@scarlehoff does this works for you with homebrew?

[scarrazza]

I have the suspicious that Python3_LINK_OPTIONS could fix this problem but I did not manage to find how.

[scarlehoff]

tbh, I think the c interface might be simple enough to skip the complexity introduced by cmake...

I haven't had the mac the last few days, I'll try it out and see whether I can fix it.

[scarlehoff]

The problem you are seeing is due to DYLD_LIBRARY_PATH=${VIRTUAL_ENV}/lib:${DYLD_LIBRARY_PATH}

I'd add it as a comment to the readme. There's another problem in mac os when running under virtual environments, but it is also a "non-problem" in the sense that a long as the executable is in ${VIRTUAL_ENV}/bin it works ok. For some reason mac and linux set sys.executable differently and, reading this I would say that Mac's way is a bug.

[scarlehoff]

updated the readme, the problem with sys.executable I wouldn't bother...

[scarrazza]

Anyway, I think we can merge this given that also linux needs those changes in order to compile successfully.

[scarlehoff]

Ok for me. I did test it in Linux and it works.