tests/pkg_libhydrogen: test fails on master for the samr21-xpro with LLVM

[bergzand]

Description

One of the runtime test in the libhydrogen tests fails with LLVM on the samr21-xpro. This is causing one of the failures in the RIOT nightlies for some days now. Commit to blame (according to a bisect) seems to be 81cb769 from #14754.

Steps to reproduce the issue

BUILD_IN_DOCKER=1 make -C tests/pkg_libhydrogen/ BOARD=samr21-xpro  TOOLCHAIN=llvm flash term

Expected results

2020-09-23 13:31:53,251 # START
2020-09-23 13:31:53,257 # main(): This is RIOT! (Version: 2020.10-devel-1507-g97a0b-HEAD)
2020-09-23 13:31:53,585 # ...
2020-09-23 13:31:53,586 # OK (3 tests)

Actual results

2020-09-23 13:32:26,209 # START
2020-09-23 13:32:26,215 # main(): This is RIOT! (Version: 2020.10-devel-1507-g97a0b-HEAD)
2020-09-23 13:32:28,005 # ...
2020-09-23 13:32:28,014 # libhydrogen_tests.test_hydro_secretbox_encryptdecrypt (tests/pkg_libhydrogen/main.c 68) res == 0
2020-09-23 13:32:28,014 # 
2020-09-23 13:32:28,016 # run 3 failures 1

Versions

The versions from the docker image

[bergzand]

I can only reproduce this in the docker container, my local LLVM (clang version 10.0.1) can't reproduce the issue