[safe-stack] Fix typo in test command line

Author: vitalybuka

llvm/test/Transforms/SafeStack/X86/no-crash-on-lifetime.ll

@@ -1,4 +1,5 @@
-; RUN: opt -safe-stack -S -mtriple=x86_64-pc-linux-gnu < %s -o -d
+; Check that the pass does not crash on the code.
+; RUN: opt -safe-stack -S -mtriple=x86_64-pc-linux-gnu %s -o /dev/null
 
 %class.F = type { %class.o, i8, [7 x i8] }
 %class.o = type <{ i8*, i32, [4 x i8] }>