add a trailing slash (otbQgisDescritor won't do it for you)

otb/OTBAlgorithmProvider.py

@@ -85,7 +85,7 @@ class OTBAlgorithmProvider(QgsProcessingProvider):
                 if not os.path.exists(dfile):
                     cmdlist = [os.path.join(folder,'bin', 'otbQgisDescriptor'),
                                    app_name, app_dir,
-                                   os.path.join(folder, 'descriptors')]
+                                   os.path.join(folder, 'descriptors/')]
                     commands = ' '.join(cmdlist)
                     QgsMessageLog.logMessage(self.tr(commands), self.tr('Processing'), Qgis.Critical)
                     OTBUtils.executeOtb(commands, feedback=None)