bug#29866: 27.0.50; cl-loop: Calculate the array length just once

[Drew Adams]

> >> (let* ((--cl-var-- 'foo)
> >>        (--cl-var-- 'bar))
> >
> > That's the same variable, `--cl-var--', bound
> > first to `foo' and then to `bar'.
> 
> That's a printout using print-circle and/or print-gensym set to nil.  If
> those were set to t, you would get something that could be properly read
> back as lisp code, e.g.:
> 
>     (let* ((#1=#:--cl-var-- 'foo)
>            (#2=#:--cl-var-- 'bar))
>        (frobnicate #1# #2#))

Ah, thanks.  That wasn't clear.  Sorry for the noise.