Allow creating logger instances on the Wine side

So we can log filterable messages from the Wine side. Will be used to
warn about failed query interface calls.

src/common/logging/common.cpp

@@ -80,6 +80,25 @@ Logger Logger::create_from_environment(std::string prefix) {
     }
 }
 
+Logger Logger::create_wine_stderr() {
+    auto env = boost::this_process::environment();
+    std::string verbosity =
+        env[logging_verbosity_environment_variable].to_string();
+
+    Verbosity verbosity_level;
+    try {
+        verbosity_level = static_cast<Verbosity>(std::stoi(verbosity));
+    } catch (const std::invalid_argument&) {
+        verbosity_level = Verbosity::basic;
+    }
+
+    // We're logging directly to `std::cerr` instead of to `/dev/stderr` because
+    // we want the STDERR redirection from the group host processes to still
+    // function here
+    return Logger(std::shared_ptr<std::ostream>(&std::cerr), verbosity_level,
+                  "");
+}
+
 void Logger::log(const std::string& message) {
     const auto current_time = std::chrono::system_clock::now();
     const std::time_t timestamp =

src/common/logging/common.h

@@ -85,6 +85,13 @@ class Logger {
      */
     static Logger create_from_environment(std::string prefix = "");
 
+    /**
+     * Create a special logger instance that outputs directly to STDERR without
+     * any prefixes. This is used to be able to log filterable messages from the
+     * Wine side of things.
+     */
+    static Logger create_wine_stderr();
+
     /**
      * Write a message to the log, prefixing it with a timestamp and this
      * logger's prefix string.