On current master, I'm seeing strange behaviour when trying to
suppress warnings in the test suite using with-suppressed-warnings.

(See also related bug Bug#36567 -- not sure if it's a duplicate.
Please merge if it is.)

Steps to reproduce:
0. Apply attached patch bug-suppressed-warnings.diff
1. Open shell
2. cd emacs/test
3. rm lisp/emacs-lisp/seq-tests.elc
4. make lisp/emacs-lisp/seq-tests

Result:
  ELC      lisp/emacs-lisp/seq-tests.elc

In toplevel form:
lisp/emacs-lisp/seq-tests.el:183:20:Warning: `seq-contains' is an obsolete
    function (as of 27.1); use `seq-contains-p' instead.
lisp/emacs-lisp/seq-tests.el:183:20:Warning: `seq-contains' is an obsolete
    function (as of 27.1); use `seq-contains-p' instead.
lisp/emacs-lisp/seq-tests.el:183:20:Warning: `seq-contains' is an obsolete
    function (as of 27.1); use `seq-contains-p' instead.
[...]

Expected result:
No such warnings appear.


In GNU Emacs 27.0.50 (build 2, x86_64-apple-darwin15.6.0, NS
appkit-1404.47 Version 10.11.6 (Build 15G22010))
 of 2019-07-10 built on Stefans-MBP
Repository revision: 77cf71ce8cc611ecfd143277441e2ad4acc9401b
Repository branch: master
Windowing system distributor 'Apple', version 10.3.1404
System Description:  Mac OS X 10.11.6