WL#10344: Remove disabling of strict aliasing optimization (GCC)

SysQA performance testing has shown 0-4% performance improvement in Sysbench by
re-enabling strict aliasing optimization. The largest improvement was in
single-threaded performance. No negative consequences (performance, stability)
have been seen.

User Documentation
==================

https://dev.mysql.com/doc/relnotes/mysql/8.0/en/news-8-0-2.html