Add dummy Platform::Integration on Linux.

Telegram/SourceFiles/platform/linux/integration_linux.cpp

@@ -7,3 +7,18 @@ https://github.com/telegramdesktop/tdesktop/blob/master/LEGAL
 */
 #include "platform/linux/integration_linux.h"
 
+#include "platform/platform_integration.h"
+
+namespace Platform {
+namespace {
+
+class LinuxIntegration final : public Integration {
+};
+
+} // namespace
+
+std::unique_ptr<Integration> CreateIntegration() {
+	return std::make_unique<LinuxIntegration>();
+}
+
+} // namespace Platform