[NFC] Extract the code to write instr profile into function writeInstrProfile

[wmi]

Summary

So that the function writeInstrProfile can be used in other places, for example in https://reviews.llvm.org/D81981.

[davidxl]

lgtm

llvm/tools/llvm-profdata/llvm-profdata.cpp

Dst->Writer.mergeRecordsFromWriter(std::move(Src->Writer), [&](Error E) {
     instrprof_error IPE = InstrProfError::take(std::move(E));
     std::unique_lock<std::mutex> ErrGuard{Dst->ErrLock};
     bool firstTime = Dst->WriterErrorCodes.insert(IPE).second;
     if (firstTime)
       warn(toString(make_error<InstrProfError>(IPE)));
   });
 }
 
+static void writeInstrProfile(StringRef OutputFilename,
+                              ProfileFormat OutputFormat,
+                              InstrProfWriter &Writer) {
+  std::error_code EC;
+  raw_fd_ostream Output(OutputFilename.data(), EC, sys::fs::OF_None);
+  if (EC)
+    exitWithErrorCode(EC, OutputFilename);
+
+  if (OutputFormat == PF_Text) {
+    if (Error E = Writer.writeText(Output))
+      exitWithError(std::move(E));
+  } else {
+    Writer.write(Output);
+  }
+}
+
 static void mergeInstrProfile(const WeightedFileVector &Inputs,
                               SymbolRemapper *Remapper,
                               StringRef OutputFilename,
                               ProfileFormat OutputFormat, bool OutputSparse,
                               unsigned NumThreads, FailureMode FailMode) {
   if (OutputFilename.compare("-") == 0)
     exitWithError("Cannot write indexed profdata format to stdout.");
 
for (auto &ErrorPair : WC->Errors) {
       ++NumErrors;
       warn(toString(std::move(ErrorPair.first)), ErrorPair.second);
     }
   }
   if (NumErrors == Inputs.size() ||
       (NumErrors > 0 && FailMode == failIfAnyAreInvalid))
     exitWithError("No profiles could be merged.");
 
-  std::error_code EC;
-  raw_fd_ostream Output(OutputFilename.data(), EC, sys::fs::OF_None);
-  if (EC)
-    exitWithErrorCode(EC, OutputFilename);
-
-  InstrProfWriter &Writer = Contexts[0]->Writer;
-  if (OutputFormat == PF_Text) {
-    if (Error E = Writer.writeText(Output))
-      exitWithError(std::move(E));
-  } else {
-    Writer.write(Output);
-  }
+  writeInstrProfile(OutputFilename, OutputFormat, Contexts[0]->Writer);
 }
 
 /// Make a copy of the given function samples with all symbol names remapped
 /// by the provided symbol remapper.
 static sampleprof::FunctionSamples
 remapSamples(const sampleprof::FunctionSamples &Samples,
              SymbolRemapper &Remapper, sampleprof_error &Error) {
   sampleprof::FunctionSamples Result;