Fix loading FriBiDi on Alpine

[nulano]

Testing python-pillow/pillow-wheels#271, I find the tests pass, but Raqm is not enabled even when I install FriBiDi.

On Alpine, fribidi is at /usr/lib/libfribidi.so.0, and I can see the second dlopen call succeeds when using strace. However, the shim is still rejecting the SO. This is because the dlerror call returns the error for the first dlopen call.

This could be fixed by calling dlerror before retrying to clear the error, but since all dlsym return values are checked to be non-null, there is actually no need to check dlerror at all.

See PR adding tests in python-pillow/pillow-wheels#274

[hugovk]

Should this be reported/contributed upstream?

[nulano]

Should this be reported/contributed upstream?

No, this my code written for Pillow (in #5062). I added dlerror because that was used in the previous implementation (dynamically loading Raqm in _imagingft.c) which this was based on.

[hugovk]

Thanks!