hardware_irq in host mode is missing a dependency on hardware_claim

[rhulme]

hardware_irq uses functions from hardware_claim but does not include the dependency in CMakeLists.txt.

Normally, hardware_claim would be added automatically as a dependency by anything calling pico_simple_hardware_impl_target but the dependency is explicitly not added there if not building for hardware. It's not entirely clear why as hardware_claim does not access any hardware.

[rhulme]

I'm happy to create a PR to either add the dependency explicitly to host/hardware_irq, or to remove the explicit exclusion in the base CMakeLists.txt (in pico_simple_hardware_impl_target and pico_simple_hardware_headers_target) depending on what you consider to be the correct solution.