[lldb][COFF] Try to detect GNU ABI by checking for DWARF debug info

[alvinhochun]

Summary

If the object file contains any DWARF debug info or a gnu-debuglink
section, it is likely using the GNU ABI. If the default target is MSVC,
we should set the module triple to GNU in this case.

• Fixes https://github.com/llvm/llvm-project/issues/50775
• Fixes https://github.com/mstorsjo/llvm-mingw/issues/226
• Fixes https://github.com/mstorsjo/llvm-mingw/issues/282

Depends on D127048

lldb/source/Plugins/ObjectFile/PECOFF/ObjectFilePECOFF.cpp

static llvm::Triple::EnvironmentType default_env = [] {
     auto def_target = llvm::Triple(
         llvm::Triple::normalize(llvm::sys::getDefaultTargetTriple()));
     if (def_target.getOS() == llvm::Triple::Win32 &&
         def_target.getEnvironment() != llvm::Triple::UnknownEnvironment)
       return def_target.getEnvironment();
     return llvm::Triple::MSVC;
   }();
 
+  llvm::Triple::EnvironmentType env = default_env;
+  if (default_env == llvm::Triple::MSVC) {
+    // If there is DWARF debug info or gnu_debuglink, then it is very likely
+    // not using the MSVC C++ ABI.
+    bool has_dwarf_debug = false;
+    for (const auto &sec : COFFObj->sections()) {
+      if (sec.isDebugSection()) {
+        has_dwarf_debug = true;
+        break;
+      }
+      if (auto name = sec.getName()) {
+        if (*name == ".gnu_debuglink") {
+          has_dwarf_debug = true;
+          break;
+        }
+      }
+    }
+    if (has_dwarf_debug)
+      env = llvm::Triple::GNU;
+  }
+
   switch (COFFObj->getMachine()) {
   case MachineAmd64:
     spec.SetTriple("x86_64-pc-windows");
-    spec.GetTriple().setEnvironment(default_env);
+    spec.GetTriple().setEnvironment(env);
     specs.Append(module_spec);
     break;
   case MachineX86:
     spec.SetTriple("i386-pc-windows");
-    spec.GetTriple().setEnvironment(default_env);
+    spec.GetTriple().setEnvironment(env);
     specs.Append(module_spec);
     spec.SetTriple("i686-pc-windows");
-    spec.GetTriple().setEnvironment(default_env);
+    spec.GetTriple().setEnvironment(env);
     specs.Append(module_spec);
     break;
   case MachineArmNt:
     spec.SetTriple("armv7-pc-windows");
-    spec.GetTriple().setEnvironment(default_env);
+    spec.GetTriple().setEnvironment(env);
     specs.Append(module_spec);
     break;
   case MachineArm64:
     spec.SetTriple("aarch64-pc-windows");
-    spec.GetTriple().setEnvironment(default_env);
+    spec.GetTriple().setEnvironment(env);
     specs.Append(module_spec);
     break;
   default:
     break;
   }
 
   return specs.GetSize() - initial_count;
 }