Stop mybuild generating CI noises

[haochenx]

• prompted by #24884
• should be a fix: mybuild: conflicts with bytecode only compilers #24937

Affected distros:

• arm32-ocaml-5.1
• ocaml-5.1-afl
• ppc64-ocaml-5.1
• x86_32-ocaml-5.1

[haochenx]

@ygrek do you mind to look at the CI log and see whether they can be fixed upstream?

If a fix cannot be easily achieved we can also mark them as unavailable on those distros (or, if it's a problem with the CI containers, we can mark them to be ignored on the CI infrastructure)

[ygrek]

thanks, i will check (and i should probably just get rid of mybuild altogether)

[mseri]

mybuild metadata has been updated fixing this issue

[ygrek]

new release should fix this #26039