The run-clang-tidy.py helper script is supposed to be used by the
user, hence it should be placed in the user's PATH. Some
distributions, like Gentoo , won't have it in PATH unless it is
installed in bin/.
Furthermore, installed scripts in PATH usually do not carry a filename
extension, since there is no need to know that this is a Python
script. For example Debian and Ubuntu already install this script as
'run-clang-tidy'  and hence build systems like Meson also look for
this name first . Hence we install run-clang-tidy.py as
run-clang-tidy, as suggested by Sylvestre Ledru .