[PATCH libinput] doc: update build instructions for Arch

[Eric Engestrom]

`abs` has been deprecated, and shut down last month. [1]
`asp` replaces it, so rewrite the instructions to use this instead.

Also, add `--noextract` to the makepkg command, as there is no point
downloading and extracting the sources since they're not going to be
built here.

[1] https://www.archlinux.org/news/deprecation-of-abs/

Signed-off-by: Eric Engestrom <eric.engestrom at imgtec.com>
---
 doc/building.dox | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/doc/building.dox b/doc/building.dox
index 5ce2146..355c535 100644
--- a/doc/building.dox
+++ b/doc/building.dox
@@ -124,10 +124,11 @@ $> sudo zypper modifyrepo --disable `zypper repos | grep source | awk '{print $5
 </li>
 <li><b>Arch</b>:
 <pre>
-$> abs extra/libinput
+$> sudo pacman -S asp
 $> cd $(mktemp -d)
+$> asp export libinput
-$> cp /var/abs/extra/libinput/PKGBUILD .
+$> cd libinput
-$> makepkg --syncdeps --nobuild
+$> makepkg --syncdeps --nobuild --noextract
 </pre>
 </li>
 </ul>
-- 
Cheers,
  Eric