kanshi: fix exec configuration

Also add a test case for the exec option.

PR #1446

modules/services/kanshi.nix

@@ -120,7 +120,7 @@ let
     ''
       profile ${name} {
         ${concatStringsSep "\n  " (map outputStr outputs)}
-    '' + optionalString (exec != null) "  ${exec}" + ''
+    '' + optionalString (exec != null) "  exec ${exec}\n" + ''
       }
     '';
 in {

tests/modules/services/kanshi/basic-configuration.conf

@@ -2,6 +2,7 @@ profile desktop {
   output "eDP-1" disable
   output "Iiyama North America PLE2483H-DP" enable position 0,0
   output "Iiyama North America PLE2483H-DP 1158765348486" enable mode 1920x1080 position 1920,0 scale 2.100000 transform flipped-270
+  exec echo "1 two 3"
 }
 
 profile nomad {

tests/modules/services/kanshi/basic-configuration.nix

@@ -11,6 +11,7 @@
           }];
         };
         desktop = {
+          exec = ''echo "1 two 3"'';
           outputs = [
             {
               criteria = "eDP-1";