GCC 8 Updates, master branch (2019.07.10.)

This is a sibling of !510 (merged). The only reason why I couldn't just cherry-pick that MR is that the C++ standard selection in AtlasLCG is different between the 1.0 and master branches.

See !510 (merged) for more details, but in short, these updates are supposed to make our builds more robust, and less "noisy".

AE Build SUCCESS
Build logfiles are available at Jenkins [AE-MERGE-REQUEST-CC7 #45]

merged

mentioned in commit 9429272d