Back when this was added, we weren't using sysroots, and we did end up
with host binaries that couldn't run on the host because libstdc++ came
along the host compiler, and was newer than the system libstdc++. These
concerns are long gone (libstdc++ in the sysroots is older than any
supported linux host build system), so we don't need to run those checks
anymore.
Differential Revision: https://phabricator.services.mozilla.com/D182691
