edksetup.sh, BaseTools/BuildEnv: add --reconfig support

Add command line option --reconfig to edksetup.sh, forcing cached
copies of Conf/*.txt to be overwritten.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Leif Lindholm <leif.lindholm@linaro.org>
Reviewed-by: Liming Gao <liming.gao@intel.com>

BaseTools/BuildEnv

@@ -3,6 +3,7 @@
 # This file must be "sourced" not merely executed. For example: ". edksetup.sh"
 #
 # Copyright (c) 2006 - 2015, Intel Corporation. All rights reserved.<BR>
+# Copyright (c) 2016, Linaro Ltd. All rights reserved.<BR>
 # This program and the accompanying materials
 # are licensed and made available under the terms and conditions of the BSD License
 # which accompanies this distribution.  The full text of the license may be found at
@@ -215,7 +216,7 @@ CopySingleTemplateFile() {
 
   if [ -e $DST_FILENAME ]
   then
-    return
+    [ $RECONFIG != TRUE ] && return
   fi
 
   echo "Copying \$EDK_TOOLS_PATH/$SRC_FILENAME"