add the file extension for minidumps on windows

Change-Id: Ib5692ef839c500cac7d2551d0b0ee6faf141132a

desktop/source/app/sofficemain.cxx

@@ -89,7 +89,7 @@ static bool dumpCallback(const wchar_t* path, const wchar_t* id,
     std::ofstream minidump_file(ini_path, std::ios_base::app);
     // TODO: moggi: can we avoid this conversion
     std::wstring_convert<std::codecvt_utf8<wchar_t>> conv1;
-    std::string aPath = conv1.to_bytes(std::wstring(path)) + conv1.to_bytes(std::wstring(id));
+    std::string aPath = conv1.to_bytes(std::wstring(path)) + conv1.to_bytes(std::wstring(id)) + ".dmp";
     minidump_file << "DumpFile=" << aPath << "\n";;
     minidump_file.close();
     SAL_WARN("desktop", "minidump generated: " << aPath);