BaseTools/BuildEnv: override "set -C" (noclobber) in sourcing shell env

The BuildEnv utility is sourced (executed by the user's interactive shell)
when the user sets up the build session. Some users like to set -C
(noclobber) for some additional safety in their shells, which trips up
BuildEnv. Update the redirection operator so that it overrides noclobber.

Cc: Liming Gao <[email protected]>
Cc: Thomas Huth <[email protected]>
Cc: Yonghong Zhu <[email protected]>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Laszlo Ersek <[email protected]>
Reviewed-by: Liming Gao <[email protected]>
Reviewed-by: Thomas Huth <[email protected]>

BaseTools/BuildEnv

@@ -90,7 +90,7 @@ StoreCurrentConfiguration() {
   #
   OUTPUT_FILE=$CONF_PATH/BuildEnv.sh
   #echo Storing current configuration into $OUTPUT_FILE
-  echo "# Auto-generated by ${BASH_SOURCE[0]}" > $OUTPUT_FILE
+  echo "# Auto-generated by ${BASH_SOURCE[0]}" >| $OUTPUT_FILE
   GenerateShellCodeToSetVariable WORKSPACE $OUTPUT_FILE
   GenerateShellCodeToSetVariable EDK_TOOLS_PATH $OUTPUT_FILE
   GenerateShellCodeToUpdatePath $OUTPUT_FILE