Sema: fix coerceResultPtr

It did not handle properly when the dummy operand was a comptime_int; it
was crashing in coerce because comptime_int is supposed to be
comptime-known. So when calling coerceResultPtr, we pass the actual
operand, not a dummy operand, which means it will have the proper
comptime value when necessary.

test/behavior/array.zig

@@ -570,10 +570,7 @@ test "type coercion of pointer to anon struct literal to pointer to array" {
 }
 
 test "array with comptime only element type" {
-    const a = [_]type{
-        u32,
-        i32,
-    };
+    const a = [_]type{ u32, i32 };
     try testing.expect(a[0] == u32);
     try testing.expect(a[1] == i32);
 }