UT-3125 Relative path of texture fix (#534)

Temp file now created in same directory as final fbx to fix relative path reference in fbx file.

Author: natalia-wh

com.unity.formats.fbx/Editor/FbxExporter.cs

@@ -3438,17 +3438,23 @@ internal int ExportAll (
             Dictionary<GameObject, IExportData> exportData)
         {
             exportCancelled = false;
+            
+            m_lastFilePath = LastFilePath;
 
             // Export first to a temporary file
             // in case the export is cancelled.
             // This way we won't overwrite existing files.
-            try{
-                m_tempFilePath = Path.GetTempFileName();
+            try
+            {
+                // create a temp file in the same directory where the fbx will be exported
+                var exportDir = Path.GetDirectoryName(m_lastFilePath);
+                var lastFileName = Path.GetFileName(m_lastFilePath);
+                var tempFileName = Path.GetFileNameWithoutExtension(Path.GetRandomFileName()) + "_" + lastFileName;
+                m_tempFilePath = Path.Combine(new string[] { exportDir, tempFileName });
             }
             catch(IOException){
                 return 0;
             }
-            m_lastFilePath = LastFilePath;
 
             if (string.IsNullOrEmpty (m_tempFilePath)) {
                 return 0;