Register core_application logger as default logger

So that logs made without an explicit logger are done using
this logger.

Change-Id: Ifd454e9ede1c89548827c073b847ea9ad191a22b
Reviewed-on: https://codereview.kdab.com/c/kdab/kdutils/+/136291
Reviewed-by: Sean Harmer <[email protected]>
Reviewed-by: Mike Krus <[email protected]>
Tested-by: Continuous Integration <[email protected]>

src/KDFoundation/core_application.cpp

@@ -39,6 +39,7 @@ CoreApplication::CoreApplication(std::unique_ptr<AbstractPlatformIntegration> &&
         m_logger = KDUtils::Logger::logger("application");
         m_logger->set_level(spdlog::level::info);
     }
+    spdlog::set_default_logger(m_logger);
 
     // Helps with debugging setup on remote hosts
     if (const char *display = std::getenv("DISPLAY"))