ams: support building unit test programs on windows/linux/macos

kern/test: add wip qemu-virt board support to mesosphere

kern: enable lto for global instants (saves about a page in deduplicated code)

kern: put rela in bss ...

NOTE: This saves ~0x4000 of space at the cost of crimes against the linker script.

Meso build targets (#1196) ...

* meso: commit wip (thanks fincs) rewrite to support build targets

* meso: commit mostly-working build system

* meso: correct .o dependencies in kernel/kldr

* libstratosphere: fix building after PCH related build changes

Co-authored-by: fincs <fincs@devkitpro.org>

kern: fix built-in usage for libc

ams: update build system to add generic-fallback support

meso: skeleton buildsystem for kernel