db845c-userdebug: Enable booting AOSP with GBL

Enable booting AOSP from mmc-sdcard on DB845c and RB5 with
Generic Bootloader Library (GBL).

Set TARGET_USES_GBL=true at the build time (depends on
TARGET_SDCARD_BOOT=true) to build GBL compatible (boot image
header v4) AOSP images.

Smoke tested AOSP with upstream GBL (bootable/libbootloader
HEAD:f7529b301c64 gbl: libgbl: src: decompress.rs: fix magic
number of gzip) on DB845c and RB5 running U-Boot 2025.04-rc5
fork.

Howto build and flash instructions are updated at
https://devboardsforandroid.linaro.org/en/latest/devices/rb3.html
and
https://devboardsforandroid.linaro.org/en/latest/devices/rb5.html

We are setting a couple of critical androidboot.* bootargs
as kernel cmdline arguments along with bootconfig to
workaround a bug in the older GBL code which fails to set
those variables and device doesn't boot.

Change-Id: I7968fe3ac6f921693b1d4030f3c993db0356afea
Signed-off-by: Amit Pundir <amit.pundir@linaro.org>
[jstultz: Cherry picked from https://r.android.com/3501470]
Signed-off-by: John Stultz <jstultz@google.com>
2 files changed