[arch-dev-public] PKGBUILD.com devtools

[Jan Steffens]

Our PKGBUILD.com build server is now tentatively running my devtools patchset.

User-visible changes should be:
--- *-build now always requires sudo. This used to be inconsistent,
requiring sudo only for -c.
--- All chroots are now kept in /var/tmp/archbuild, a btrfs volume.
--- All chroot copies are kept in btrfs subvolumes.
--- makechrootpkg will now name the chroot copy after your username
instead of simply "copy", e.g. /var/tmp/archbuild/extra-x86_64/johndoe
--- mkarchroot and makechrootpkg will lock chroots that are in use.
This means builds using the same chroot copy will be serialized
instead of simply failing.

TLDR: You should be able to continue using the devtools helpers as
usual. Just note: *-build requires sudo, chroots are in
/var/tmp/archbuild.

Please report any problems.