fix(main/libluajit): strip git hash from autoupdate timestamp.

[TomJo2000]

The LuaJIT auto-update was broken, again. This time by Arch starting to append the commit hash to the version. I think that's a good idea, so I have adopted that here.

I've also fixed up the timestamp comment for the TERMUX_PKG_VERSION. This works locally, but will need further testing before I'm satisfied that it works as intended.