[arch-general] How to build package in "clean chroot" using the "-U" parameter?

[Manuel Reimer]

Hello,

I want to autobuild a set of packages. For this process, it is not 
acceptable to use "sudo" as I don't want to enter some passwords and my 
autobuild program also has to do some other stuff with root privileges.

The help page of "makechrootpkg" suggests, that there is an option for me:

-U         Run makepkg as a specified user

But I tried this several times. So far without success.

I've copied the PKGBUILD to the /tmp directory, just to be sure it is 
really readable by my build user.

Then my command was:

# makechrootpkg -c -U build -r /var/cache/PATH_TO_MY_CHROOT

This now seems to download the source files and also is validating them 
against the stored MD5 sums.

But after that I get the error

==> ERROR: Running makepkg as root is not allowed as it can cause 
permanent, catastrophic damage to your system.

Seems like makepkg is called once in context of my supplied "build user" 
and then a second time without using the build user.

Where is my mistabe? Or is this a bug in makechrootpkg?

Thanks in advance

Manuel