test failures when building 2.2.53 with -flto=auto -O3

[Matthias Klose]

I have seen
https://lists.nongnu.org/archive/html/acl-devel/2020-08/msg00000.html

but when building with -flto -O3, I see again test failures withing the acl
testsuite.

https://launchpadlibrarian.net/530709491/buildlog_ubuntu-hirsute-s390x.acl_2.2.53-10build1_BUILDING.txt.gz

while the log is for s390x, these failures can be reproduced on x86_64-linux-gnu
as well.

Building with -flto=auto -O3 -fno-strict-aliasing lets the tests succeed, so I
assume this is another aliasing issue.

Compiler used is current gcc-10 branch.

Matthias