[llvm-objcopy,test] Prepend error: to some messages

Author: MaskRay

llvm/test/tools/llvm-objcopy/ELF/discard-locals-rel.test

@@ -1,5 +1,5 @@
 # RUN: yaml2obj %s -o %t
-# RUN: not llvm-objcopy --discard-locals %t %t2 2>&1 | FileCheck %s
+# RUN: not llvm-objcopy --discard-locals %t %t2 2>&1 | FileCheck %s -DFILE=%t
 
 !ELF
 FileHeader:
@@ -23,4 +23,4 @@ Symbols:
     Type:     STT_FUNC
     Section:  .text
 
-# CHECK: not stripping symbol '.L.rel' because it is named in a relocation
+# CHECK: error: '[[FILE]]': not stripping symbol '.L.rel' because it is named in a relocation

llvm/test/tools/llvm-objcopy/ELF/strip-reloc-symbol.test

@@ -1,5 +1,5 @@
 # RUN: yaml2obj %s -o %t
-# RUN: not llvm-objcopy -N foo %t %t2 2>&1 | FileCheck %s
+# RUN: not llvm-objcopy -N foo %t %t2 2>&1 | FileCheck %s -DFILE=%t
 
 !ELF
 FileHeader:
@@ -28,4 +28,4 @@ Symbols:
     Value:    0x1000
     Size:     8
 
-# CHECK: not stripping symbol 'foo' because it is named in a relocation
+# CHECK: error: '[[FILE]]': not stripping symbol 'foo' because it is named in a relocation