internal/system: optional op check parallelism

The PipeWire Op check cannot be made parallel due to the OS interaction.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/system/dispatcher_test.go

@@ -36,17 +36,26 @@ type opBehaviourTestCase struct {
 	wantErrRevert error
 }
 
-func checkOpBehaviour(t *testing.T, testCases []opBehaviourTestCase) {
+const (
+	// checkNoParallel causes checkOpBehaviour to skip setting tests as parallel.
+	checkNoParallel = 1 << iota
+)
+
+func checkOpBehaviour(t *testing.T, flags int, testCases []opBehaviourTestCase) {
 	t.Helper()
 
 	t.Run("behaviour", func(t *testing.T) {
 		t.Helper()
-		t.Parallel()
+		if flags&checkNoParallel == 0 {
+			t.Parallel()
+		}
 
 		for _, tc := range testCases {
 			t.Run(tc.name, func(t *testing.T) {
 				t.Helper()
-				t.Parallel()
+				if flags&checkNoParallel == 0 {
+					t.Parallel()
+				}
 
 				var ec *Criteria
 				if tc.ec != 0xff {