[libcalamares] All commands with workingDirectory failed

- This is the same as EFAIL: a block is indented as if it's a multi-
   line else block. This isn't Python though, and the return always
   applies.
 - Add the necessary braces.
 - Apparently noone uses this code path (until ProcessJob was re-
   factored to do so).

src/libcalamares/utils/CalamaresUtilsSystem.cpp

@@ -202,8 +202,10 @@ System::runCommand(
         if ( QDir( workingPath ).exists() )
             process.setWorkingDirectory( QDir( workingPath ).absolutePath() );
         else
+        {
             cWarning() << "Invalid working directory:" << workingPath;
             return ProcessResult::Code::NoWorkingDirectory;
+        }
     }
 
     cDebug() << "Running" << program << RedactedList( arguments );