Change in coreboot[master]: payloads/external/LinuxBoot: Adopt u-root change

[Patrik Tesarik (Code Review)]

Hello Patrick Georgi, Martin Roth, Christian Walter,  Marcello Sylvester Bauer,

I'd like you to reexamine a change. Please visit

https://review.coreboot.org/c/coreboot/+/40316

to look at the new patch set (#9).

Change subject: payloads/external/LinuxBoot: Adopt u-root change
......................................................................

payloads/external/LinuxBoot: Adopt u-root change

The u-root toolkit dropped the original uinit bootloader in the master
branch and respectively the systemboot-option in templates.go. In consequence
the LinuxBoot builds will boot into the u-root shell and waiting for input.
This commit enables the reuse of the -uinitcmd flag to specify a command, which
runs after the u-root init-process.

Systemboot as a bootloader wrapper will mimick a BIOS/UEFI boot device
selection and hence is, as of this design change, implemented as the
favoured option for an -uinitcmd in contrast to the default value,
which will be a boot into the u-root shell. Other preselections, i.e. stboot
and boot2 are implemented as well. Custom strings or programs can be set
as well, but they cannot contain program flags. E.g. 'fbnetboot -class
linuxboot' will not work, because they aren't symlinkable.

This commit and its respective LinuxBoot builds with systemboot, none
and one custom option have been tested successfully on a UP squared
single board computer with the intended behavior.

Change-Id: I4ac3409040ea77a1836f90f43fba07d2cd05a952
Signed-off-by: Patrik Tesarik 
---
M payloads/external/LinuxBoot/Kconfig
M payloads/external/LinuxBoot/targets/u-root.mk
M payloads/external/Makefile.inc
3 files changed, 61 insertions(+), 2 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/16/40316/9