Migrate clang-version-inc.py to python3

Bug: 203436762
Test: ./clang-version-inc.py include/clang/Basic/Version.inc.in
Test: ./clang-version-inc.py
Change-Id: I5bdf726063c6d5281a97debeac9cea47251ecc4d
(cherry picked from commit f16728514b601312ea4f62a4dd3af7112b4768d9)
Merged-In: I5bdf726063c6d5281a97debeac9cea47251ecc4d
Bug: 247129589
1 file changed