apply_copyright script is not portable

[dgovil]

Running apple_copyright from within the root of the package on macOS 14 gives me the following error

src/build_utils/license/apply_copyright
xargs: invalid option -- i
usage: xargs [-0opt] [-E eofstr] [-I replstr [-R replacements] [-S replsize]]
             [-J replstr] [-L number] [-n number [-x]] [-P maxprocs]
             [-s size] [utility [argument ...]]
xargs: invalid option -- i
usage: xargs [-0opt] [-E eofstr] [-I replstr [-R replacements] [-S replsize]]
             [-J replstr] [-L number] [-n number [-x]] [-P maxprocs]
             [-s size] [utility [argument ...]]

I believe this is assuming a GNU/Linux configuration of xargs which is not compatible with the BSD/Darwin version of xargs