Merge pull request #189314 from Artturin/addemulatoravailable

lib/systems/default.nix

@@ -158,8 +158,10 @@ rec {
         if final.isMacOS then "MACOSX_DEPLOYMENT_TARGET"
         else if final.isiOS then "IPHONEOS_DEPLOYMENT_TARGET"
         else null;
-
-      emulator = pkgs: let
+    } // (
+      let
+        selectEmulator = pkgs:
+          let
             qemu-user = pkgs.qemu.override {
               smartcardSupport = false;
               spiceSupport = false;
@@ -187,9 +189,16 @@ rec {
           then "${pkgs.wasmtime}/bin/wasmtime"
           else if final.isMmix
           then "${pkgs.mmixware}/bin/mmix"
+          else null;
+      in {
+        emulatorAvailable = pkgs: (selectEmulator pkgs) != null;
+
+        emulator = pkgs:
+          if (final.emulatorAvailable pkgs)
+          then selectEmulator pkgs
           else throw "Don't know how to run ${final.config} executables.";
 
-    } // mapAttrs (n: v: v final.parsed) inspect.predicates
+    }) // mapAttrs (n: v: v final.parsed) inspect.predicates
       // mapAttrs (n: v: v final.gcc.arch or "default") architectures.predicates
       // args;
   in assert final.useAndroidPrebuilt -> final.isAndroid;