For now, compile all of contrib/gdtoa without requiring strict aliasing,
since it is using type punning of union members, and clang does not yet
support gcc's extensions which allow this (refer to
https://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html#Type%2dpunning
for more information).

This should fix strtod(3) return values for the lang/julia port, so it
does not fail on an assertion during its build.

PR: 216770