Install ShairPort on Arch on a Rpi

gistfile1.sh

#!/usr/bin/env bash +xe
# Assumes a sane-ish system with git and wget

pacman -S --noconfirm avahi libao openssl perl-crypt-openssl-rsa perl-io-socket-inet6 perl-libwww 

wget https://aur.archlinux.org/packages/pe/perl-net-sdp/perl-net-sdp.tar.gz
tar -zxvf perl-net-sdp.tar.gz
pushd perl-net-sdp
  makepkg -s --asroot
  pacman -U perl-net-sdp-*.pkg.tar.xz
popd
rm -rf perl-net-sdp*

pacman -S --noconfirm alsa-utils alsa-firmware alsa-lib alsa-plugins

git clone https://github.com/abrasive/shairport.git shairport
pushd shairport
  make
  make install
popd
rm -rf shairport

cat > /etc/systemd/system/shairport.service << "EOF"
[Unit]
Description=Startup ShairPort (Apple AirPlay)
After=network.target
After=avahi-daemon.service

[Service]
Type=oneshot
ExecStart=/usr/local/bin/shairport -a Irradiated -b 256 -d
ExecStop=/usr/bin/killall shairport
RemainAfterExit=yes

[Install]
WantedBy=multi-user.target
EOF

systemctl enable avahi-daemon
systemctl enable shairport

Nice, worked for me (except the shebangline).
But maybe it is a little bit cleaner to tell systemd, that we are using a daemon so that it could keep track of failures of the forked shairport process. My systemd service looks like this:

[Unit]
Description=Startup ShairPort (Apple AirPlay)
After=network.target
After=avahi-daemon.service

[Service]
Type=forking
PIDFile=/var/run/shairport.pid
ExecStart=/usr/local/bin/shairport --daemon --pidfile=/var/run/shairport.pid 
ExecStop=/usr/bin/kill $MAINPID

[Install]
WantedBy=multi-user.target