Dear Maintainer,

this package fails to execute its buildtime tests (dh_auto_test) on the s390x
architecture when compiled with an LTO enabled toolchain. On Ubuntu
(GCC-12 + LTO) we saw the following failure.

This does not directly affect Debian, but might, should Debian enable LTO by
default in the future. Please consider disabling LTO explicitly to avoid such
(future) failure, or feel free to reject this patch if you feel like it doesn't
apply.

In Ubuntu, the attached patch was applied to achieve the following:

  * d/rules: Disable LTO, to avoid FTBFS (test failure) on s390x


Thanks for considering the patch.
-------------------------------------------------------------------------------
Test value store
  store supports swap
-------------------------------------------------------------------------------
./libpotassco/tests/test_value.cpp:95
...............................................................................

./libpotassco/tests/test_value.cpp:100: FAILED:
  REQUIRE( Po::value_cast<Counted>(x).parsed == 10 )
with expansion:
  0 == 10

===============================================================================
test cases:  16 |  15 passed | 1 failed
assertions: 127 | 126 passed | 1 failed

<end of output>
Test time =   1.00 sec
----------------------------------------------------------
Test Failed.
"test_opts" end time: Apr 12 14:19 UTC
"test_opts" time elapsed: 00:00:01
----------------------------------------------------------

End testing: Apr 12 14:19 UTC

==> build.dir/hardening_mt/Testing/Temporary/LastTestsFailed.log <==
2:test_opts
make[1]: *** [debian/rules:49: override_dh_auto_test] Error 25
make[1]: Leaving directory '/<<PKGBUILDDIR>>'
make: *** [debian/rules:29: binary-arch] Error 2
dpkg-buildpackage: error: debian/rules binary-arch subprocess returned exit status 2
--------------------------------------------------------------------------------
Build finished at 2023-04-12T14:19:21Z