tests/libc_newlib: blacklist esp32 boards temporarily

[gschorcht]

Contribution description

ESP32 boards must be blacklisted for tests/libc_newlib to avoid CI compilation errors until the toolchain is updated on all nodes. This change has to be reverted by merging PR #13812 once all nodes are update.

Testing procedure

Compilation in Murdock has to succeed.

Issues/PRs references

[benpicco]

Is this still needed?
When @cgundogan said the update takes a while I was expecting a couple of hours, not days - a couple of hours have passed and #13812 is passing

[cgundogan]

When @cgundogan said the update takes a while I was expecting a couple of hours, not days - a couple of hours have passed and #13812 is passing

not all pods form the haw-icc have yet transitioned to the new docker image. That's unfortunately out of my hands. 10 from the 16 pods still need to update the docker image.

But I am still unsure if breeze and riotbuild updated the image (@kaspar030 and @aabadie can say more here). Nevertheless, most of our nodes are up-to-date. So merging this PR will do more good then harm.

[cgundogan]

So merging this PR will do more good then harm.

I meant merging the other PR.

[gschorcht]

Merging this PR would solve the problem that the compilations for all PRs fail at the moment. If we would then merge PR #13812 in one or two days, everything should be fine.

[benpicco]

Well alright then, if building with #13812 is not reliable yet we should probably merge this, so Murdock isn't enforcing a hard feature freeze 😉