*converter: join --plugin-dir with a relative search path, not absolute.

Now it finally works again.

src/Magnum/SceneTools/sceneconverter.cpp

@@ -310,7 +310,7 @@ is specified as well, the IDs reference attributes of the first mesh.)")
 
     PluginManager::Manager<Trade::AbstractImporter> importerManager{
         args.value("plugin-dir").empty() ? Containers::String{} :
-        Utility::Path::join(args.value("plugin-dir"), Trade::AbstractImporter::pluginSearchPaths()[0])};
+        Utility::Path::join(args.value("plugin-dir"), Trade::AbstractImporter::pluginSearchPaths().back())};
 
     Containers::Pointer<Trade::AbstractImporter> importer = importerManager.loadAndInstantiate(args.value("importer"));
     if(!importer) {
@@ -1100,7 +1100,7 @@ is specified as well, the IDs reference attributes of the first mesh.)")
     /* Load converter plugin */
     PluginManager::Manager<Trade::AbstractSceneConverter> converterManager{
         args.value("plugin-dir").empty() ? Containers::String{} :
-        Utility::Path::join(args.value("plugin-dir"), Trade::AbstractSceneConverter::pluginSearchPaths()[0])};
+        Utility::Path::join(args.value("plugin-dir"), Trade::AbstractSceneConverter::pluginSearchPaths().back())};
 
     /* Assume there's always one passed --converter option less, and the last
        is implicitly AnySceneConverter. All converters except the last one are

src/Magnum/ShaderTools/shaderconverter.cpp

@@ -353,7 +353,7 @@ see documentation of a particular converter for more information.)")
     /* Set up a converter manager */
     PluginManager::Manager<ShaderTools::AbstractConverter> converterManager{
         args.value("plugin-dir").empty() ? Containers::String{} :
-        Utility::Path::join(args.value("plugin-dir"), ShaderTools::AbstractConverter::pluginSearchPaths()[0])};
+        Utility::Path::join(args.value("plugin-dir"), ShaderTools::AbstractConverter::pluginSearchPaths().back())};
 
     /* Data passed from one converter to another in case there's more than one */
     Containers::Array<char> data;

src/Magnum/Text/fontconverter.cpp

@@ -164,12 +164,12 @@ int FontConverter::exec() {
     /* Font converter dependencies */
     PluginManager::Manager<Trade::AbstractImageConverter> imageConverterManager{
         args.value("plugin-dir").empty() ? Containers::String{} :
-        Utility::Path::join(args.value("plugin-dir"), Trade::AbstractImageConverter::pluginSearchPaths()[0])};
+        Utility::Path::join(args.value("plugin-dir"), Trade::AbstractImageConverter::pluginSearchPaths().back())};
 
     /* Load font */
     PluginManager::Manager<Text::AbstractFont> fontManager{
         args.value("plugin-dir").empty() ? Containers::String{} :
-        Utility::Path::join(args.value("plugin-dir"), Text::AbstractFont::pluginSearchPaths()[0])};
+        Utility::Path::join(args.value("plugin-dir"), Text::AbstractFont::pluginSearchPaths().back())};
     Containers::Pointer<Text::AbstractFont> font = fontManager.loadAndInstantiate(args.value("font"));
     if(!font) return 1;
 
@@ -177,7 +177,7 @@ int FontConverter::exec() {
        (MagnumFontConverter needs TgaImageConverter, for example) */
     PluginManager::Manager<Text::AbstractFontConverter> converterManager{
         args.value("plugin-dir").empty() ? Containers::String{} :
-        Utility::Path::join(args.value("plugin-dir"), Text::AbstractFontConverter::pluginSearchPaths()[0])};
+        Utility::Path::join(args.value("plugin-dir"), Text::AbstractFontConverter::pluginSearchPaths().back())};
     converterManager.registerExternalManager(imageConverterManager);
 
     /* Load font converter */

src/Magnum/Trade/imageconverter.cpp

@@ -363,7 +363,7 @@ key=true; configuration subgroups are delimited with /.)")
 
     PluginManager::Manager<Trade::AbstractImporter> importerManager{
         args.value("plugin-dir").empty() ? Containers::String{} :
-        Utility::Path::join(args.value("plugin-dir"), Trade::AbstractImporter::pluginSearchPaths()[0])};
+        Utility::Path::join(args.value("plugin-dir"), Trade::AbstractImporter::pluginSearchPaths().back())};
 
     const Int dimensions = args.value<Int>("dimensions");
     /** @todo make them array options as well? */
@@ -901,7 +901,7 @@ key=true; configuration subgroups are delimited with /.)")
     /* Load converter plugin */
     PluginManager::Manager<Trade::AbstractImageConverter> converterManager{
         args.value("plugin-dir").empty() ? Containers::String{} :
-        Utility::Path::join(args.value("plugin-dir"), Trade::AbstractImageConverter::pluginSearchPaths()[0])};
+        Utility::Path::join(args.value("plugin-dir"), Trade::AbstractImageConverter::pluginSearchPaths().back())};
     Containers::Pointer<Trade::AbstractImageConverter> converter = converterManager.loadAndInstantiate(args.value("converter"));
     if(!converter) {
         Debug{} << "Available converter plugins:" << ", "_s.join(converterManager.aliasList());