BEFORE:
the python derivation did not contain .nativeDrv and .crossDrv because
it was not from the __splicedPackages set
the python used in mk-python-derivation.nix was for host
```
nix-repl> pkgsCross.aarch64-multiplatform.python3Packages.xpybutil.nativeBuildInputs
[ «derivation /nix/store/bhz39ds4v02hn6x4py4mzjyilw4a589h-python3-aarch64-unknown-linux-gnu-3.10.7.drv» «derivation /nix/store/v880cnh4ml7czmivfbk3cdh93hz9yvbn-hook.drv» «derivation /nix/store/f243ab7wv92gqsmc9h7gr0qcnj0xcgdb-hook.drv» «derivation /nix/store/880lf8895bzn8d94lrr2y7ilgkxq0lc4-python-remove-tests-dir-hook.drv» «derivation /nix/store/fzjnhawfs1wpw58hcd1vxd9y750dc08y-python-remove-bin-bytecode-hook.drv» «derivation /nix/store/n8l59iparx98yfw8g5ydqmzmk3fdic75-setuptools-setup-hook.drv» «deri→
```
AFTER:
the python derivation does contain .nativeDrv and .crossDrv because
it is from the __splicedPackages set
those 2 are what makes nativeBuildInputs and buildInputs function
properly
the python used in mk-python-derivation.nix is for build
```
nix-repl> pkgsCross.aarch64-multiplatform.python3Packages.xpybutil.nativeBuildInputs
[ «derivation /nix/store/hvb9yxgv1133cfhxxd869sibldvv2vdx-python3-3.10.7.drv» «derivation /nix/store/v880cnh4ml7czmivfbk3cdh93hz9yvbn-hook.drv» «derivation /nix/store/f243ab7wv92gqsmc9h7gr0qcnj0xcgdb-hook.drv» «derivation /nix/store/880lf8895bzn8d94lrr2y7ilgkxq0lc4-python-remove-tests-dir-hook.drv» «derivation /nix/store/fzjnhawfs1wpw58hcd1vxd9y750dc08y-python-remove-bin-bytecode-hook.drv» «derivation /nix/store/n8l59iparx98yfw8g5ydqmzmk3fdic75-setuptools-setup-hook.drv» «derivation /nix/store/7vyhynla→
```
Test with:
nix-build -A lua.tests pass
Tests are very limited for now, goal is mostly to put the infra into
place and enrich the tests when dealing with lua issues.
add luaPath/luaCpath as passthrough
makes it easier to generate LUA_PATH/LUA_CPATH
Since the Nix command used is an implementation detail of the script,
it's the script that will have to be updated if the command changes,
it's the script that should be opting into this, rather than making
the user do it globally.
Since c0972c16dc ("update-python-libraries: add missing dependency nix"),
Nix will be provided as a dependency, so we know we'll always be using
a modern version and no longer need the fallback.
