buildPython*: store dist (wheel/sdist) in dist output

Store the intermediate artifacts. In time, we should build, install and
test in separate derivations as that reduces circular dependencies,
avoids rebuilds when fixing tests, and makes it possible to use the
wheels for creating say virtualenv's.

pkgs/development/interpreters/python/hooks/python-output-dist-hook.sh

@@ -0,0 +1,10 @@
+# Setup hook for storing dist folder (wheels/sdists) in a separate output
+echo "Sourcing python-catch-conflicts-hook.sh"
+
+pythonOutputDistPhase() {
+    echo "Executing pythonOutputDistPhase"
+    mv "dist" "$dist"
+    echo "Finished executing pythonOutputDistPhase"
+}
+
+preFixupPhases+=" pythonOutputDistPhase"