[NFC] Make a test more debuggable

Author: beccadax

test/IRGen/prespecialized-metadata/class-fileprivate-inmodule-1argument-2ancestor-1du-1st_ancestor_generic-fileprivate-2nd_ancestor_nongeneric.swift

@@ -1,6 +1,7 @@
 // RUN: %empty-directory(%t)
 
-// RUN: %target-swift-frontend -prespecialize-generic-metadata -target %module-target-future -emit-ir -I %t -L %t %s | %FileCheck %s -DINT=i%target-ptrsize -DALIGNMENT=%target-alignment --check-prefix=CHECK --check-prefix=CHECK-%target-vendor
+// RUN: %target-swift-frontend -prespecialize-generic-metadata -target %module-target-future -emit-ir -I %t -L %t %s > %t/out.ir
+// RUN: %FileCheck --input-file=%t/out.ir %s -DINT=i%target-ptrsize -DALIGNMENT=%target-alignment --check-prefix=CHECK --check-prefix=CHECK-%target-vendor
 
 // REQUIRES: VENDOR=apple || OS=linux-gnu
 // UNSUPPORTED: CPU=i386 && OS=ios