BaseTools: Update windows and linux run scripts file to use Python3

Modify windows script, PosixLike script, edksetup.sh, edksetup.bat to
use Python3

Cc: Liming Gao <liming.gao@intel.com>
Cc: Yonghong Zhu <yonghong.zhu@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Yunhua Feng <yunhuax.feng@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>

edksetup.sh

@@ -111,10 +111,41 @@ function SetupEnv()
   fi
 }
 
+function SetupPython3()
+{
+  for python in $(whereis python3)
+  do
+    python=$(echo $python | grep "[[:digit:]]$" || true)
+    python_version=${python##*python}
+    if [ -z "${python_version}" ];then
+      continue
+    fi
+    if [ -z $origin_version ];then
+      origin_version=$python_version
+      export PYTHON3=$python
+      continue
+    fi
+    ret=`echo "$origin_version < $python_version" |bc`
+    if [ "$ret" -eq 1 ]; then
+      origin_version=$python_version
+      export PYTHON3=$python
+    fi
+  done
+  if [ -z "$origin_version" ] || [ `echo "$origin_version < 3.6" |bc` -eq 1 ]; then
+    echo
+    echo ERROR!!!, python version should greater than or equal to version 3.6.
+    echo 
+    return 1
+  fi
+
+ 
+}
+
 function SourceEnv()
 {
   SetWorkspace &&
   SetupEnv
+  SetupPython3
 }
 
 I=$#