-fno-strict-aliasing required on GCC

I'm not exactly sure what the problem is yet, because the library doesn't seem to actually commit any aliasing crimes at all...!

...But we were getting occasional incorrect results on our Linux builds, and we found that adding the `-fno-strict-aliasing` flag to GCC fixed these weird errors.

The issue names no files, tests, or entry points. Start by reproducing the incorrect Linux GCC results with and without -fno-strict-aliasing, then identify the cause and define done as correct results without relying on that compiler flag.

Written by the indexing model from the issue text.