talloc: fix cross-compilation to 32-bit platforms

pkgs/development/libraries/talloc/default.nix

@@ -1,6 +1,6 @@
 { stdenv
 , fetchurl
-, python
+, python3
 , pkg-config
 , readline
 , libxslt
@@ -10,7 +10,7 @@
 , wafHook
 }:
 
-stdenv.mkDerivation rec {
+stdenv.mkDerivation (rec {
   pname = "talloc";
   version = "2.3.1";
 
@@ -22,13 +22,14 @@ stdenv.mkDerivation rec {
   nativeBuildInputs = [
     pkg-config
     fixDarwinDylibNames
-    python
+    python3
     wafHook
     docbook-xsl-nons
     docbook_xml_dtd_42
   ];
 
   buildInputs = [
+    python3
     readline
     libxslt
   ];
@@ -56,4 +57,9 @@ stdenv.mkDerivation rec {
     license = licenses.gpl3;
     platforms = platforms.all;
   };
-}
+} // stdenv.lib.optionalAttrs (stdenv.hostPlatform != stdenv.buildPlatform) {
+  # python-config from build Python gives incorrect values when cross-compiling.
+  # If python-config is not found, the build falls back to using the sysconfig
+  # module, which works correctly when cross-compiling.
+  PYTHON_CONFIG = "/invalid";
+})