There were some issues with the current Linuxboot Makefiles. - multithreaded compilation didn't work, because some prerequisites were missing - initramfs wasn't added for x86 qemu boot. - riscv support was incomplete It began with separate patches, but resulted in a clean up patch, that is hard to separate. The most important changes are the following: - Instead of phony targets, actual files are now used as prerequisites - riscv can now be used as target - initramfs works now also for x86 - instead of querying the most recent version from the internet, I set a known working version (because I tested it) that can be customized and/or upgraded in the future. The reasons: - querying the version from the internet requires a constant connection to the internet even after linux kernel is already build (aka subsequent builds). - one usually wants to use a known working version, but optionally still have the posibillity to choose a custom one. This patch introduces this possibility in its most simple form. - I removed as much ifeq statements as possible and moved that responsibility to Kconfig, because they tend to make the Makefile less readable. Signed-off-by: Maximilian Brune <maximilian.brune@9elements.com> Change-Id: I25e757108e0dd473969fe5a192ad0733f1fe6286 Reviewed-on: https://review.coreboot.org/c/coreboot/+/76150 Reviewed-by: Lean Sheng Tan <sheng.tan@9elements.com> Tested-by: build bot (Jenkins) <no-reply@coreboot.org>