Send output to a temp file, even in the error case

Prior to this, the test tries to write to the source directory,
which prevents it from working when the source is on a read-only
file systems.

Author: Sterling-Augustine

llvm/test/CodeGen/X86/apx/asm-constraint-2-jR.ll

@@ -1,8 +1,8 @@
 ; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
-; RUN: not llc -mtriple=x86_64 %s 2>&1 | FileCheck %s --check-prefix=ERR
+; RUN: not llc -mtriple=x86_64 %s -o %t 2>&1 | FileCheck %s --check-prefix=ERR
 ; RUN: llc -mtriple=x86_64 -mattr=+egpr < %s | FileCheck %s
 ; RUN: llc -mtriple=x86_64 -mattr=+egpr,+inline-asm-use-gpr32 < %s | FileCheck %s
-; RUN: not llc -mtriple=x86_64 -mattr=+inline-asm-use-gpr32 %s 2>&1 | FileCheck %s --check-prefix=ERR
+; RUN: not llc -mtriple=x86_64 -mattr=+inline-asm-use-gpr32 %s -o %t 2>&1 | FileCheck %s --check-prefix=ERR
 
 ; ERR: error: inline assembly requires more registers than available