uml: drop target

[Bastian Bittorf]

On Sun, Oct 10, 2021 at 12:23:16PM -0400, Michael Richardson wrote:
> I haven't used the UML target in the past year, but I have used it a lot
> before.
> The ability to do hostfs mounts is very nice.
> If it went away, I'd be sad, it's not a disaster as you say.

I'am also an infrequent user. I do not see an issue
for the moment, it compiles and runs just fine:

bastian at ubuntu:~/software/openwrt$ bin/targets/uml/generic/openwrt-uml-vmlinux ubd0=bin/targets/uml/generic/openwrt-uml-squashfs.img eth8=tuntap,,,192.168.0.254
Core dump limits :
        soft - 0
        hard - NONE
Checking that ptrace can change system call numbers...OK
Checking syscall emulation patch for ptrace...OK
Checking advanced syscall emulation patch for ptrace...OK
Checking environment variables for a tempdir...none found
Checking if /dev/shm is on tmpfs...OK
Checking PROT_EXEC mmap in /dev/shm...OK
Adding 19591168 bytes to physical memory to account for exec-shield gap
[    0.000000] Linux version 5.4.152 (bastian at ubuntu) (gcc version 10.2.0 (Ubuntu 10.2.0-13ubuntu1)) #0 Thu Oct 14 17:40:03 2021
[    0.000000] Built 1 zonelists, mobility grouping on.  Total pages: 12772
[...]

root at OpenWrt:/ :) cat /proc/cpuinfo 
processor       : 0
vendor_id       : User Mode Linux
model name      : UML
mode            : skas
host            : Linux ubuntu 5.8.0-25-generic #26-Ubuntu SMP Thu Oct
15 10:30:38 UTC 2020 x86_64
bogomips        : 3321.03

root at OpenWrt:/ :) cat /etc/openwrt_release 
DISTRIB_ID='OpenWrt'
DISTRIB_RELEASE='SNAPSHOT'
DISTRIB_REVISION='r17755+24-0eed96ca5d'
DISTRIB_TARGET='uml/generic'
DISTRIB_ARCH='x86_64'
DISTRIB_DESCRIPTION='OpenWrt SNAPSHOT r17755+24-0eed96ca5d'
DISTRIB_TAINTS='no-all busybox'