Change `bytes!()` to return
{
static BYTES: &'static [u8] = &[...];
BYTES
}
This gives it the `'static` lifetime, whereas before it had an rvalue
lifetime. Until recently this would have prevented assigning `bytes!()`
to a static, as in
static FOO: &'static [u8] = bytes!(1,2,3);
but #14183 fixed it so blocks are now allowed in constant expressions
(with restrictions).
Fixes #11641.