imgtool: Update version.py to take command line arguments

Main method printed hardcoded versions, update to take argument
to enable the possibility of testing version strings by invoking
the command through command line.

Signed-off-by: Rustam Ismayilov <rustam.ismayilov@arm.com>
Change-Id: If75769ef223944865313ed95336e859ebef85fd6
diff --git a/scripts/imgtool/version.py b/scripts/imgtool/version.py
index 6e38f44..b803834 100644
--- a/scripts/imgtool/version.py
+++ b/scripts/imgtool/version.py
@@ -1,4 +1,5 @@
 # Copyright 2017 Linaro Limited
+# Copyright 2024 Arm Limited
 #
 # SPDX-License-Identifier: Apache-2.0
 #
@@ -20,9 +21,9 @@
 Implements a subset of semantic versioning that is supportable by the image
 header.
 """
-
-from collections import namedtuple
 import re
+import sys
+from collections import namedtuple
 
 SemiSemVersion = namedtuple('SemiSemVersion', ['major', 'minor', 'revision',
                                                'build'])
@@ -49,7 +50,7 @@
 
 
 if __name__ == '__main__':
-    print(decode_version("1.2"))
-    print(decode_version("1.0"))
-    print(decode_version("0.0.2+75"))
-    print(decode_version("0.0.0+00"))
+    if len(sys.argv) > 1:
+        print(decode_version(sys.argv[1]))
+    else:
+        print("Requires an argument, e.g. '1.0.0'")