It doesn't have to, you just add a zero byte at the end of the embedded byte sequence in the object file. It's up to the programmer to make the choice how to interpret that.

That said for binary embeds you almost always need the length embedded as well, which has been the case for every tool I've used to embed files in object code. You usually get something like

    const size_t My_FILE_LENGTH = ... ;
    const uint8_t MY_FILE[] = { ... };