Fix cmake version detection from git tag.

Tools/tag_to_version.py

@@ -0,0 +1,17 @@
+import subprocess
+import os
+import argparse
+
+p = argparse.ArgumentParser('finds major minor patch version from git tag')
+p.add_argument('--root', help="root of git repo", default=".")
+args = p.parse_args()
+os.chdir(args.root)
+p= subprocess.Popen(
+    'git describe --always --tags'.split(),
+    stdout=subprocess.PIPE, stderr=subprocess.PIPE)
+stdout, stderr = p.communicate()
+res = stdout.split('-')[0].split('.')
+major = res[0].replace('v','')
+minor = res[1]
+patch = res[2]
+print("{:s}.{:s}.{:s}".format(major, minor, patch))