Why are these CI builds failing? What should I do about them?

Hi @GabeNI,
I think your PR is fine.

Those errors are caused by the following reasons. I'll fix these tests soon. Sorry!

• As for gcc-11

  • g++-11 has been removed from GitHub Actions default environment.

• As for gcc-{4.7, 4.6, 4.4} and clang-{3.8, 3.7, 3.6, 3.5}

  • apt-get failed to retrieve some package.
  • We should add apt-get update for all apt-gets.

Yes, as stated by @t-mat , this is unrelated, and fixed in a separate PR