Generate same output on all architectures.

Passing an argument to bug260 will indicate which alignments
are wrong.

R=r
CC=golang-dev
https://golang.org/cl/231042

test/bugs/bug260.go

-// $G $D/$F.go && $L $F.$A && ./$A.out
+// $G $D/$F.go && $L $F.$A && ./$A.out || echo BUG: bug260 failed
 
 // Test that structures pack densely, according to the alignment of the largest field.
 
@@ -15,27 +15,41 @@ type T2 struct { x uint16 }
 type T4 struct { x uint32 }
 
 func main() {
+	report := len(os.Args) > 1
 	status := 0
 	var b1 [10]T1
 	a0, _ := strconv.Btoui64(fmt.Sprintf("%p", &b1[0])[2:], 16)
 	a1, _ := strconv.Btoui64(fmt.Sprintf("%p", &b1[1])[2:], 16)
 	if a1 != a0 + 1 {
-		fmt.Println("FAIL: alignment should be 1, is", a1-a0)
+		fmt.Println("FAIL")
+		if report {
+			fmt.Println("alignment should be 1, is", a1-a0)
+		}
 		status = 1
 	}
 	var b2 [10]T2
 	a0, _ = strconv.Btoui64(fmt.Sprintf("%p", &b2[0])[2:], 16)
 	a1, _ = strconv.Btoui64(fmt.Sprintf("%p", &b2[1])[2:], 16)
 	if a1 != a0 + 2 {
-		fmt.Println("FAIL: alignment should be 2, is", a1-a0)
+		if status == 0 {
+			fmt.Println("FAIL")
 			status = 1
 		}
+		if report {
+			fmt.Println("alignment should be 2, is", a1-a0)
+		}
+	}
 	var b4 [10]T4
 	a0, _ = strconv.Btoui64(fmt.Sprintf("%p", &b4[0])[2:], 16)
 	a1, _ = strconv.Btoui64(fmt.Sprintf("%p", &b4[1])[2:], 16)
 	if a1 != a0 + 4 {
-		fmt.Println("FAIL: alignment should be 4, is", a1-a0)
+		if status == 0 {
+			fmt.Println("FAIL")
 			status = 1
 		}
+		if report {
+			fmt.Println("alignment should be 4, is", a1-a0)
+		}
+	}
 	os.Exit(status)
 }

test/golden.out

@@ -152,6 +152,5 @@ panic PC=xxx
 == bugs/
 
 =========== bugs/bug260.go
-FAIL: alignment should be 1, is 8
-FAIL: alignment should be 2, is 8
-FAIL: alignment should be 4, is 8
+FAIL
+BUG: bug260 failed