interop: enable preserveArgvZero

Fixes interop with latest WSL versions

Author: K900

modules/wsl-distro.nix

@@ -67,8 +67,28 @@ with builtins; with lib;
         binfmt.registrations = mkIf cfg.interop.register {
           WSLInterop = {
             magicOrExtension = "MZ";
-            interpreter = "/init";
+
+            # FIXME: temporary hack for https://github.com/nix-community/NixOS-WSL/pull/84
+            #
+            # WSL Preview 0.58 and up registers the /init binfmt interp for Windows executable
+            # with the "preserve argv[0]" flag, so if you run `./foo.exe`, the interp gets invoked
+            # as `/init foo.exe ./foo.exe`.
+            #   argv[0] --^        ^-- actual path
+            #
+            # Older versions expect to be called without the argv[0] bit, simply as `/init ./foo.exe`.
+            #
+            # We detect that by running `/init /known-not-existing-path.exe` and checking the exit code:
+            # the new style interp expects at least two arguments, so exits with exit code 1,
+            # presumably meaning "parsing error"; the old style interp attempts to actually run
+            # the executable, fails to find it, and exits with 255.
+            interpreter = pkgs.writeShellScript "nixos-wsl-binfmt-hack" ''
+              /init /nixos-wsl-does-not-exist.exe
+              [ $? -eq 255 ] && shift
+              exec /init $@
+            '';
+
             fixBinary = true;
+            preserveArgvZero = true;
           };
         };
       };