examples: conditionally compile an `asm amd64 {}` block on M1 in asm.v

examples/asm.v

@@ -2,6 +2,7 @@ fn main() {
 	a := 100
 	b := 20
 	mut c := 0
+	$if amd64 {
 		asm amd64 {
 			mov eax, a
 			add eax, b
@@ -10,6 +11,7 @@ fn main() {
 			; r (a) // input
 			  r (b)
 		}
+	}
 	println('a: $a') // 100
 	println('b: $b') // 20
 	println('c: $c') // 120