Global: Make additional upgrades from GCC5 to GCC

Following on from the previous commit upgrading the CI from GCC5 to GCC,
in this commit we make the same upgrade in additional locations where it
appears appropriate.

Potential candidates discovered by simple `grep -r GCC5` in the project.

Continuous-integration-options: PatchCheck.ignore-multi-package

Signed-off-by: Mike Beaton <mjsbeaton@gmail.com>
4 files changed