Reapply r238941 - [dsymutil] Accept a YAML debug map as input instead of a binary.

With a couple more constructors that GCC thinks are necessary.

Original commit message:

[dsymutil] Accept a YAML debug map as input instead of a binary.

To do this, the user needs to pass the new -y flag.
As it wasn't tested before, the debug map YAML deserialization was
completely buggy (mainly because the DebugMapObject has a dual
mapping that allows to search by name and by address, but only the
StringMap got populated). It's fixed and tested in this commit by
augmenting some test with a 2 stage dwarf link: a frist llvm-dsymutil
reads the debug map and pipes it in a second instance that does the
actual link without touching the initial binary.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@238959 91177308-0d34-0410-b5e6-96231b3b80d8

tools/dsymutil/MachODebugMapParser.cpp

@@ -242,12 +242,32 @@ void MachODebugMapParser::loadMainBinarySymbols() {
   }
 }
 
+ErrorOr<std::unique_ptr<DebugMap>>
+parseYAMLDebugMap(StringRef InputFile, bool Verbose) {
+  auto ErrOrFile = MemoryBuffer::getFileOrSTDIN(InputFile);
+  if (auto Err =ErrOrFile.getError())
+    return Err;
+
+  std::unique_ptr<DebugMap> Res;
+  yaml::Input yin((*ErrOrFile)->getBuffer());
+  yin >> Res;
+
+  if (auto EC = yin.error())
+    return EC;
+
+  return std::move(Res);
+}
+
 namespace llvm {
 namespace dsymutil {
 llvm::ErrorOr<std::unique_ptr<DebugMap>>
-parseDebugMap(StringRef InputFile, StringRef PrependPath, bool Verbose) {
-  MachODebugMapParser Parser(InputFile, PrependPath, Verbose);
-  return Parser.parse();
+parseDebugMap(StringRef InputFile, StringRef PrependPath, bool Verbose, bool InputIsYAML) {
+  if (!InputIsYAML) {
+    MachODebugMapParser Parser(InputFile, PrependPath, Verbose);
+    return Parser.parse();
+  } else {
+    return parseYAMLDebugMap(InputFile, Verbose);
+  }
 }
 }
 }