tests/unittests: Fix error due to macOS sed incompatibility

[x3ro]

Since most people™ seem to be developing on linux machines, they
commonly have gnu sed installed. In my experience with cross-platform
projects, it makes sense to require installation of gnu-sed on macOS
since dealing with the incompatibilites of sed is non-trivial.

This commit introduces such a check for the relic package.

For reference, the imcompatible sed call is located in
pkg/relic/fix-util_print_wo_args.sh (e.g. in 775e207)

This loosely relates to #6473.

[kYc0o]

Wow! I'm working exactly on the same thing. However, I'm looking for a "real" solution by making work OS X sed -i '' as it should. Did you try that?

[kYc0o]

I just found the problem. It's a locale thing, we need just to set LC_CTYPE=C in the os_util.sh script under pkg/relic.

[kYc0o]

Do you mind to change your commit or you prefer that I make another PR with this solution? (of course if this solution works for you as well). @smlng Can you check if my proposed solution doesn't break anything for you? IIRC you didn't have any problem with this package.

[jnohlgard]

Is it possible to install the MacOS sed and other tools on Linux, to be able to test these kinds of things on Linux?
I mean is the source available somewhere?

[smlng]

I fixed that in the past #6105, did someone update relic and changed the usage of sed?

[smlng]

@gebart typically macOS uses non-gnu variant of command, maybe openbsd ships them?

[smlng]

I like #7785 better, way simpler.

[kYc0o]

I fixed that in the past #6105, did someone update relic and changed the usage of sed?

No, there was no change in the code, I think it just stop working on newer versions of OS X.

[smlng]

to fix relic I still prefer #7785.

We may think about fixing the general issue of incompatible (GNU vs. standard UNIX, like on macOS) shell commands in scripts used by RIOT on a higher level. However, that isn't solved here either.

What I mean is to check and verify commands like sed, readlink, etc where GNU variants have different or more parameters/options at the beginning (in some global Makefile) and check for alternative versions (like gsed on macOS), provide means to install them, or don't use such GNU specific parameters at all.

[jnohlgard]

It seems less of a hassle for the user to merge #7785 instead of this. Can this be closed?

[x3ro]

Yep, makes sense