This workaround was never exclusive to python2, and in fact only just
got fixed in the upcoming python 3.12 release. Extend the version
comparison to cover all those other cases.
Only search for and provide linkage to libpython, if the dependency
expects to be linked to it. Fixes overlinking on Linux / macOS when
pkg-config isn't installed and the sysconfig lookup is used instead.
This was correctly handled for pkg-config rather than deferring it until
use, since commit bf83274344 -- but that
handling neglected to cover sysconfig dependencies. And sysconfig would
always try to link to libpython, it just respected the dependency
configuration barely enough to allow falling back to "don't link" if
both link_libpython=False and the library wasn't found.
We have two copies of this code, and the python module one is vastly
superior, not just because it allows choosing which python executable to
base itself on. Unify this. Fixes various issues including non-Windows
support for sysconfig, and pypy edge cases.
In preparation for wholly merging the dependency handling from the
python module into dependencies.*, move the unique class definitions
from there into their new home in dependencies.python, which is
semantically convenient.
In preparation for handling more work inside dependencies.*, we need to
be able to run a PythonExternalProgram from the python dependency. Move
most of the definition -- but only the parts that have no interest in a
ModuleState -- and subclass a bit of sanity checking that we need to
handle specially when used in the module.
Eli Schwartz