pkgs/build-support: Add writePytonScript helper function

pkgs/build-support/default.nix

@@ -0,0 +1,5 @@
+final: prev:
+
+{
+  writePythonScript = final.callPackage ./writePythonScript.nix {};
+}

pkgs/build-support/writePythonScript.nix

@@ -0,0 +1,37 @@
+{
+  python3,
+  writeTextFile,
+  lib,
+}:
+
+{
+  name,
+  text,
+  runtimePackages ? ps: [],
+  pythonPackage ? python3,
+  meta ? {},
+  passthru ? {},
+  derivationArgs ? {},
+}:
+
+let
+
+  pythonWithPackages = pythonPackage.withPackages runtimePackages;
+
+in writeTextFile {
+  inherit
+    name
+    meta
+    passthru
+    derivationArgs
+    ;
+  executable = true;
+  destination = "/bin/${name}";
+  allowSubstitutes = true;
+  preferLocalBuild = false;
+  text = ''
+    #!${lib.getExe pythonWithPackages}
+
+    ${text}
+  '';
+}