There are some long-standing problems with lxml's binary packages on

some distributions. The version of libxml2 used during the building of

the binary packages didn't always sync up well with what was on the

system, and this could lead to failures in lxml and then xmlsec on

some systems. We've seen crashes and invalid checksums when this issue

occurs, in Review Board and third-party projects.
We now attempt to compile lxml against the system library, instead of

using the pre-built wheel. This also requires we install some other

system packages, and that we ensure some compilation errors are turned

into warnings (necessary for Fedora 40+).

Ran install tests for all supported distros. They all passed.