BaseTools/toolsetup: Do not set CONF_PATH when already set.

When CONF_PATH is already set, toolsetup.bat overwrites its value.
This is not the case on Linux platforms (BuildEnv) and
contra-productive when using the same Workspace across multiple
Operating Systems.
With this patch, a check is performed prior to setting the variable.
Furthermore, it will not be scanned for Conf directories in
PACKAGES_PATH directories to respect the user's choice.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Marvin Haeuser <Marvin.Haeuser@outlook.com>
Reviewed-by: Yonghong Zhu <yonghong.zhu@intel.com>
diff --git a/BaseTools/toolsetup.bat b/BaseTools/toolsetup.bat
index 76fd8bb..c1ab9bc 100755
--- a/BaseTools/toolsetup.bat
+++ b/BaseTools/toolsetup.bat
@@ -160,13 +160,16 @@
    goto skip_reconfig

 )

 

-set CONF_PATH=%WORKSPACE%\Conf

-if NOT exist %CONF_PATH% (

-  if defined PACKAGES_PATH (

-    for %%i IN (%PACKAGES_PATH%) DO (

-      if exist %%~fi\Conf (

-        set CONF_PATH=%%i\Conf

-        goto CopyConf

+if not defined CONF_PATH (

+  set CONF_PATH=%WORKSPACE%\Conf

+

+  if NOT exist %CONF_PATH% (

+    if defined PACKAGES_PATH (

+      for %%i IN (%PACKAGES_PATH%) DO (

+        if exist %%~fi\Conf (

+          set CONF_PATH=%%i\Conf

+          goto CopyConf

+        )

       )

     )

   )