LadspaManager: really only load shared library on Linux

Testing the last two characters of the filename against "so" is
insufficient as this might cover e.g. ISO files as well. Therefore
explicitely check for ".so".

Thanks to Mikobuntu for the contribution.

Closes #3289932.

src/core/ladspa_manager.cpp

@@ -61,10 +61,11 @@ ladspaManager::ladspaManager()
 		{
 			const QFileInfo & f = *file;
 			if( !f.isFile() ||
+				 f.fileName().right( 3 ).toLower() !=
 #ifdef LMMS_BUILD_WIN32
-				 f.fileName().right( 3 ).toLower() != "dll"
+													"dll"
 #else
-				 f.fileName().right( 2 ).toLower() != "so"
+				 									".so"
 #endif
 								)
 			{