[llvm-remarkutil] bitstream2yaml: Keep output file (#143220)

Keep the output file on successful exit, otherwise `llvm-remarkutil
bitstream2yaml -o filename.yaml ...` does not produce any output,
because the output file is deleted when the tool exits.

Author: tobias-stadler

llvm/test/tools/llvm-remarkutil/convert.test

@@ -1,6 +1,7 @@
-RUN: llvm-remarkutil bitstream2yaml %p/Inputs/two-remarks.bitstream -o - | FileCheck %s -strict-whitespace
-RUN: llvm-remarkutil yaml2bitstream %p/Inputs/two-remarks.yaml -o %t
-RUN: llvm-remarkutil bitstream2yaml %t -o - | FileCheck %s -strict-whitespace
+RUN: llvm-remarkutil bitstream2yaml %p/Inputs/two-remarks.bitstream -o %t.yaml
+RUN: FileCheck %s -strict-whitespace < %t.yaml
+RUN: llvm-remarkutil yaml2bitstream %p/Inputs/two-remarks.yaml -o %t.bitstream
+RUN: llvm-remarkutil bitstream2yaml %t.bitstream -o - | FileCheck %s -strict-whitespace
 
 ; CHECK: --- !Analysis
 ; CHECK-NEXT: Pass:            prologepilog

llvm/tools/llvm-remarkutil/RemarkConvert.cpp

@@ -133,6 +133,7 @@ static Error tryBitstream2YAML() {
   if (!E.isA<EndOfFileError>())
     return E;
   consumeError(std::move(E));
+  OF->keep();
   return Error::success();
 }
 } // namespace bitstream2yaml