archlinux: ship pam.d/qrexec as a replacement of using su

qrexec/Makefile

@@ -21,6 +21,8 @@ install:
 	install qubes-rpc-multiplexer $(DESTDIR)/usr/lib/qubes
 ifeq ($(shell lsb_release -is), Debian)
 	install -D -m 0644 qrexec.pam.debian $(DESTDIR)/etc/pam.d/qrexec
+else ifeq ($(shell lsb_release -is), Arch)
+	install -D -m 0644 qrexec.pam.archlinux $(DESTDIR)/etc/pam.d/qrexec
 else
 	install -D -m 0644 qrexec.pam $(DESTDIR)/etc/pam.d/qrexec
 endif

qrexec/qrexec.pam.archlinux

@@ -0,0 +1,9 @@
+#%PAM-1.0
+auth		sufficient	pam_rootok.so
+# Uncomment the following line to implicitly trust users in the "wheel" group.
+#auth		sufficient	pam_wheel.so trust use_uid
+# Uncomment the following line to require a user to be in the "wheel" group.
+#auth		required	pam_wheel.so use_uid
+auth		include		system-login
+account		include         system-login
+session		include		system-login