build: Define _BOOT_MODE once and for all in ArchitectureRules+BootRules.

Previously it was spread all around the tree, and was not defined
consistently for all boot objects (there were a number of boot modules
which did not define it, but did include headers which checked for it.)

Now, as it is handled in SetupBoot which is invoked for all boot objects,
it will be applied consistently throughout. We can thus drop the manual
additions of it from all Jamfiles.

boot/efi/x86: implement SMP detection and bootup

* move common SMP initialization code to x86/arch_smp.cpp

* factor out arch-specific SMP initialization to
arch_smp_32.cpp resp arch_smp_64.cpp

* implement smp_trampoline for x86 32-bit EFI loader

* rename SMP trampoline for x86_64 to long_smp_trampoline

* add new argument virtKernelArgs to arch_smp_boot_other_cpus
as the kernel args are not identity mapped on 32-bit architectures

Change-Id: I30d0bb1fa9bfb08f6784a2af34eb83d6b64afa57
Reviewed-on: https://review.haiku-os.org/c/haiku/+/4869
Tested-by: Commit checker robot <no-reply+buildbot@haiku-os.org>
Reviewed-by: waddlesplash <waddlesplash@gmail.com>
Reviewed-by: Fredrik Holmqvist <fredrik.holmqvist@gmail.com>

efi: Ensure MultiBootSubDirSetup runs in arch directories

* Otherwise, important HAIKU_BOOT_* flags don't make it into
the build commands.
* Ensure any external sources used by EFI get recompiled
vs reused due to potential differences in wchar length
(EFI dictates short-wchar, but no wchar's in our code)

Change-Id: I7a4a0347d39239c73fa510378e048f51be1cd360
Reviewed-on: https://review.haiku-os.org/c/haiku/+/2965
Reviewed-by: Alex von Gluck IV <kallisti5@unixzen.com>
Reviewed-by: Adrien Destugues <pulkomandy@gmail.com>

EFI: Make our haiku_loader architecture agnostic

* This is the bulk of the work. Anything else should be
minor cleanups and tweaking.
* riscv64 isn't a viable EFI platform yet.. just acting
as a stand-in to test a non-x86 EFI haiku_loader

Change-Id: Ib03de81e2b562e693987b86d7b4318209fb1c792
Reviewed-on: https://review.haiku-os.org/c/haiku/+/2256
Reviewed-by: Alex von Gluck IV <kallisti5@unixzen.com>
Reviewed-by: Adrien Destugues <pulkomandy@gmail.com>

efi: Refactor our EFI code to use fuchsia's cleaner EFI headers.

* Drop gnu-efi

Change-Id: Ib601fc8ced49b18281b6b98cf861a5aef1b9c065
Reviewed-on: https://review.haiku-os.org/c/haiku/+/2026
Reviewed-by: Alex von Gluck IV <kallisti5@unixzen.com>
Reviewed-by: Adrien Destugues <pulkomandy@gmail.com>

kernel/boot/efi: Continue breaking apart arch-specific code; hpet

* Move x86 hpet behind timer interface.
* Add a few if x86,x86_64 macros to start.cpp.

Change-Id: I583ec1b064785182e6d48dfbcd91b1bb2ead4b44
Reviewed-on: https://review.haiku-os.org/c/haiku/+/1929
Reviewed-by: Alex von Gluck IV <kallisti5@unixzen.com>

EFI: Break smp into arch subpath

Change-Id: Ia9438777f1da8ca32f93e0d85229230c809e6711
Reviewed-on: https://review.haiku-os.org/c/haiku/+/1918
Reviewed-by: Alex von Gluck IV <kallisti5@unixzen.com>
Reviewed-by: Adrien Destugues <pulkomandy@gmail.com>