I'm doing some driver work, and distribute these driver via DKMS package.
when installed on armbian, there is some problem.
Test Environment
* Board: OrangePi Plus 2E
* Armbian: 5.85
* OS: Ubuntu 18.04.2
Reproduce step
* install dkms and kernel header: `sudo apt-get install dkms linux-headers-next-sunxi`
* install some *-dkms package, acpi-call-dkms for example: `sudo apt-get install acpi-call-dkms`
* you get some error in _/var/lib/dkms/acpi-call/1.1.0/build/make.log_
```
DKMS make.log for acpi-call-1.1.0 for kernel 4.19.38-sunxi (armv7l)
Fri May 10 14:56:03 CST 2019
make: Entering directory '/usr/src/linux-headers-4.19.38-sunxi'
Makefile:619: arch//Makefile: No such file or directory
make: *** No rule to make target 'arch//Makefile'. Stop.
make: Leaving directory '/usr/src/linux-headers-4.19.38-sunxi'
```
but if you manually build with `dkms` command, it built with no error.
`sudo dkms build acpi-call/1.1.0`
then I check the source of dkms at https://github.com/dell/dkms
and found that in the postinst hook, ARCH variable is set to empty. so
`ARCH= dkms build acpi-call/1.1.0`
will get the same error as in the `apt-get install` command
but ARCH is set to arm in `/etc/environment`
finally, as manually build of *-dkms is OK, unable to auto install DKMS package is not a very big problem.