VDSO: Fixes a pretty nasty bug where we were never using the host VDSO

[Sonicadvance1]

This must have happened during a refactor or something, but since we're making a copy of the function pointers, it would have only gotten the version /prior/ to loading host VDSO symbols.

Moves the VDSO thunk definition setting to the end after VDSO symbol definitions in order to get host VDSO symbols working again.

Cherry-picked out of #3946

[neobrain]

What's the actual issue?

[Sonicadvance1]

When setting the pointers in the VDSODefinitions array, we are copying the pointers provided eg, FEX::VDSO::x64::Handler_time.

These pointers default to the glibc handlers, but the LoadHostVDSO function parses out the host vdso symbols and updates those pointers to the VDSO handlers, eg FEX::VDSO::x64::Handler_time default points to x64::glibc::time but now points to x64::VDSO::time.

So the VDSODefinitions array needs to late initialize its pointers.

[neobrain]

Ah, I was reading the description the wrong way, looking copies of VDSODefinitions[n].ThunkFunction rather than their assigned values. Thanks for the clarification!