SIL: Fix boxes test to actually emit SIB

Author: slavapestov

test/SIL/Serialization/boxes.sil

@@ -1,7 +1,7 @@
 // First parse this and then emit a *.sib. Then read in the *.sib, then recreate
 // RUN: %empty-directory(%t)
 // RUN: %target-sil-opt %s -emit-sib -o %t/tmp.sib -module-name boxes
-// RUN: %target-sil-opt %t/tmp.sib -o %t/tmp.2.sib -module-name boxes
+// RUN: %target-sil-opt %t/tmp.sib -emit-sib -o %t/tmp.2.sib -module-name boxes
 // RUN: %target-sil-opt %t/tmp.2.sib -module-name boxes | %FileCheck %s
 
 sil_stage canonical