scripts: Explicitly call out python2

At least one Linux distribution (Arch) has made python 3 the default
interpreter, and Debian and Ubuntu have expressed a desire to eventually
make this the case.  As such, invoking 'python' or '/usr/bin/python'
will possibly run python 3 instead of version 2.

Distributions have included a 'python2' link for quite some time now,
and given that we have some scripts that require python 3, we should be
explicit about those that require python 2.

In addition, be more consistent about how python is invoked, preferring
the:

  #!/usr/bin/env python2

construct rather than a hardcoded path to python.  This allows the user
to have an alternative python in their path that will be used in
preference to the system provided version.

Jira: ZEP-1548
Change-Id: I125c2af808dc268f74277bc97a092df3acad23c0
Signed-off-by: David Brown <david.brown@linaro.org>

scripts/check_link_map.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python2
 import fileinput
 import re
 import sys

scripts/checkconfig.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python2
 
 """Zephyr Check kconfigs Definitions
 

scripts/compare_footprint

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python2
 
 """
 This script help you to compare footprint results with previous commits in git.

scripts/diffconfig

@@ -1,4 +1,4 @@
-#!/usr/bin/python
+#!/usr/bin/env python2
 #
 # diffconfig - a tool to compare .config files.
 #

scripts/filter-known-issues.py

@@ -1,4 +1,4 @@
-#! /usr/bin/python
+#! /usr/bin/env python2
 import argparse
 import logging
 import mmap

scripts/size_report

@@ -1,4 +1,4 @@
-#!/usr/bin/python
+#!/usr/bin/env python2
 #
 # Copyright (c) 2016, Intel Corporation
 #

scripts/sysgen

@@ -1,4 +1,4 @@
-#! /usr/bin/env python
+#! /usr/bin/env python2
 #
 # sysgen - System Generator
 #