Issue Description

I work in an environment where we wish to use python-ldap without LibSASL support but this is currently enabled by default and cannot be disabled via setup.py arguments.

I know that one can disable LibSASL support by changing the defines options in the [_ldap] section of the setup.cfg file as alluded to (but incorrectly stated) in the python-ldap docs for building from source and I have automated this process but doing so makes the use of a pip requirements file impossible without extra code to control execution order.

I believe this problem should be addressed at the time of compiling the C library for LDAP though I'm not sure how setuptools handles this and am unsure of how to proceed. With some help understanding this process I'd be happy to contribute code to solve this problem.

Steps to Reproduce

1. Don't have SASL libraries installed
2. Run pip install python-ldap

Questions

• Am I on the right track here?
• Is there a better way to handle this?

Operating System: Any.
Python Version: >=3.6
python-ldap Version: Any.