Linux installer now builds properly on OSX

git-svn-id: http://svn.dmdirc.com/trunk@3534 00569f92-eb28-0410-84fd-f71c24880f

installer/linux/makeInstallerLinux.sh

 MD5BIN=`which md5sum`
 AWK=`which awk`
 getMD5() {
-	echo "test" | ${MD5BIN}
+	echo "test" | ${MD5BIN} -
 	if [ $? -eq 0 ]; then
 		getMD5Linux $@
 	else