Python: improve cross-compilation

This changeset allows for cross-compilation of Python packages. Packages
built with buildPythonPackage are not allowed to refer to the build
machine. Executables that have shebangs will refer to the host.

1 files changed, 5 insertions, 2 deletions

diff --git a/pkgs/development/interpreters/python/mk-python-derivation.nix b/pkgs/development/interpreters/python/mk-python-derivation.nix
index b9a6835908f95..7718bdfde5d34 100644
--- a/pkgs/development/interpreters/python/mk-python-derivation.nix
+++ b/pkgs/development/interpreters/python/mk-python-derivation.nix
@@ -77,7 +77,7 @@ let self = toPythonModule (python.stdenv.mkDerivation (builtins.removeAttrs attr
 
   buildInputs = [ wrapPython ]
     ++ lib.optional (lib.hasSuffix "zip" (attrs.src.name or "")) unzip
-    ++ lib.optional catchConflicts setuptools # If we no longer propagate setuptools
+#     ++ lib.optional catchConflicts setuptools # If we no longer propagate setuptools
     ++ buildInputs
     ++ pythonPath;
 
@@ -100,9 +100,12 @@ let self = toPythonModule (python.stdenv.mkDerivation (builtins.removeAttrs attr
     # Check if we have two packages with the same name in the closure and fail.
     # If this happens, something went wrong with the dependencies specs.
     # Intentionally kept in a subdirectory, see catch_conflicts/README.md.
-    ${python.interpreter} ${./catch_conflicts}/catch_conflicts.py
+    ${python.pythonForBuild.interpreter} ${./catch_conflicts}/catch_conflicts.py
   '' + attrs.postFixup or '''';
 
+  # Python packages built through cross-compilation are always for the host platform.
+  disallowedReferences = lib.optionals (python.stdenv.hostPlatform != python.stdenv.buildPlatform) [ python.pythonForBuild ];
+
   meta = {
     # default to python's platforms
     platforms = python.meta.platforms;