Fix arch package cross-compiling

dist/linux/arch/default.nix

@@ -1,11 +1,12 @@
 {
   pkgs,
   buildSystem,
+  hostSystem,
   releaseName,
   appImage,
 }: let
 
-  cpuArch = (pkgs.lib.systems.parse.mkSystemFromString buildSystem).cpu.name;
+  cpuArch = (pkgs.lib.systems.parse.mkSystemFromString hostSystem).cpu.name;
 
   pkgbuild = pkgs.writeText "isle-arch-PKGBUILD-${releaseName}-${cpuArch}" ''
     pkgname=isle
@@ -71,7 +72,7 @@ in
       tar -cf src.tar.zst --zstd --mode=a+rX,u+w -C root .
       cp "$src" isle
 
-      PKGEXT=".pkg.tar.zst" makepkg \
+      PKGEXT=".pkg.tar.zst" CARCH="${cpuArch}" makepkg \
         --nodeps \
         --config ${pkgs.pacman}/etc/makepkg.conf
     '';

release.nix

@@ -17,7 +17,7 @@
     }).appImage;
 
     archPkg = ((import ./dist/linux/arch) {
-      inherit pkgs buildSystem releaseName appImage;
+      inherit pkgs buildSystem hostSystem releaseName appImage;
     });
 
   in pkgs.stdenv.mkDerivation {