This modernizes the APKBUILD that was based from outdated one (still
needs GCC6) as requested in !165 (comment 133993271). Also adds a fix
to allow Xorg booting, osk-sdl doesn't work yet as it throws some ugly
faults in kernel related to fbcon.
[skip ci]: already built successfully in CI
Initial support for Xiaomi A1 aka xiaomi-tissot using LineageOS 15.1
kernel, has similar board to Xiaomi Redmi 4 aka xiaomi-mido with some
differences that had to be patched such as reversing skip_initramfs and
ignoring dm param. 16.0 kernel boots but display fb init doesn't work.
Weston boots with touch support, SSH via USB RNDIS works.
[skip ci]: this built once in CI already, good to go.
