[llvm-cov] Respect Windows line endings when parsing demangled symbols

[ikudrin]

Summary

When using a demangler on Windows, the output of llvm-cov might look like this:

  ------------------
: | int TemplateDemo<1>()
  |   10|      2|{

or like this (if it is stored into a file and then viewed in an editor):

  ------------------
  | int TemplateDemo<1>()
:
  |   10|      2|{

It results from splitting the demangler's output by \n, which keeps \r at the end of each symbol. This patch solves the issue by trimming strings of demangled symbols.

[vsk]

LGTM.

tools/llvm-cov/CodeCoverage.cpp

void CodeCoverageTool::demangleSymbols(const CoverageMapping &Coverage) {
   if (Symbols.size() != NumSymbols) {
     error("Demangler did not provide expected number of symbols");
     return;
   }
 
   // Cache the demangled names.
   unsigned I = 0;
   for (const auto &Function : Coverage.getCoveredFunctions())
-    DC.DemangledNames[Function.Name] = Symbols[I++];
+    // On Windows, lines in the demangler's output file end with "\r\n".
+    // Splitting by '\n' keeps '\r's, so cut them now.
+    DC.DemangledNames[Function.Name] = Symbols[I++].rtrim();
 }
 
 void CodeCoverageTool::writeSourceFileView(StringRef SourceFile,
                                            CoverageMapping *Coverage,
                                            CoveragePrinter *Printer,
                                            bool ShowFilenames) {
   auto View = createSourceFileView(SourceFile, *Coverage);
   if (!View) {