for 1.66 & 1.67 we were overriding the default toolset option. This
meant that gcc-cross was not being selected properly, breaking the
cross toolchain.
/cc @dtzWill
The reason is that if cross compiling (or for other reasons) python
bindings as a whole are turned off. Those two lines then trigger
assertion errors unless manually overridden for cross compilation.
This way:
1. The `enableNumpy` default respects the `enablePython deafult.
2. Cross works by default
3. Absurd manual overrides still break as they should
4. The `>= 1.65` logic is direct and not a maintaince gotcha.
