Ports: Add expat port (#628)

Author: https://github.com/kyllikki 🔰
Commit: https://github.com/SerenityOS/serenity/commit/4288cfa65aa
Pull-request: https://github.com/SerenityOS/serenity/pull/628

Ports/libexpat/fix-autoconf.patch

@@ -0,0 +1,19 @@
+--- conftools/config.sub.orig	2019-10-03 23:14:02.281000072 +0100
++++ conftools/config.sub	2019-10-03 23:14:36.896816822 +0100
+@@ -2,7 +2,7 @@
+ # Configuration validation subroutine script.
+ #   Copyright 1992-2018 Free Software Foundation, Inc.
+ 
+-timestamp='2018-02-22'
++timestamp='2019-10-03'
+ 
+ # This file is free software; you can redistribute it and/or modify it
+ # under the terms of the GNU General Public License as published by
+@@ -1364,6 +1364,7 @@
+ 	# Each alternative MUST end in a * to match a version number.
+ 	# -sysv* is not here because it comes later, after sysvr4.
+ 	-gnu* | -bsd* | -mach* | -minix* | -genix* | -ultrix* | -irix* \
++	      | -serenity* \
+ 	      | -*vms* | -sco* | -esix* | -isc* | -aix* | -cnk* | -sunos | -sunos[34]*\
+ 	      | -hpux* | -unos* | -osf* | -luna* | -dgux* | -auroraux* | -solaris* \
+ 	      | -sym* | -kopensolaris* | -plan9* \

Ports/libexpat/package.sh

@@ -0,0 +1,12 @@
+#!/bin/bash ../.port_include.sh
+port=libexpat
+version=2.2.9
+useconfigure=true
+files="https://codeload.github.com/libexpat/libexpat/tar.gz/R_2_2_9 expat-2.2.9.tar.gz"
+workdir=libexpat-R_2_2_9/expat/
+
+configure() {
+    run ./buildconf.sh
+    run patch -p 0 < fix-autoconf.patch
+    run ./"$configscript" --host=i686-pc-serenity $configopts
+}