bug#70236: Truncating only happening on 900 character long lines in *compilation* buffer

[Phil Sainty]

This will generate the same output as that perl:

(cl-loop for n from 100 to 1500 by 100 do
         (insert (number-to-string n)
                 " [\"" (make-string n (string-to-char
                                          (format "%X" (/ n 100))))
                 "\"]\n\n"))

If you write that to a file "test" in some temp dir and have
a Makefile like this:

foo:
        cat test

Then the suggested command will demonstrate the issue:

emacs -Q -f compile

What you're looking at is the difference between the "900" line
(which gets truncated) and all the other lines (which do not).

compilation-max-output-line-length is 400