contrib: add expat rules

Change-Id: I6894ed31cf128737e67b9a68f7650a438891a834
Refs: #46617

contrib/src/expat/SHA512SUMS

+2a9ad2b44b87b84087979fe4114d661838df3b03dbdcb74d590cb74096bf35ce9d5a86617b0941a2655ea441a94537bcbcd78252da92342238823be36de2d09d  expat-2.1.0.tar.gz

contrib/src/expat/rules.mak

+# EXPAT
+
+EXPAT_VERSION := 2.1.0
+EXPAT_URL := $(SF)/expat/expat-$(EXPAT_VERSION).tar.gz
+
+PKGS += expat
+ifeq ($(call need_pkg,"expat >= 1.95.0"),)
+PKGS_FOUND += expat
+endif
+
+$(TARBALLS)/expat-$(EXPAT_VERSION).tar.gz:
+	$(call download,$(EXPAT_URL))
+
+.sum-expat: expat-$(EXPAT_VERSION).tar.gz
+
+expat: expat-$(EXPAT_VERSION).tar.gz .sum-expat
+	$(UNPACK)
+	$(UPDATE_AUTOCONFIG)
+	$(MOVE)
+
+.expat: expat
+	cd $< && $(HOSTVARS) ./configure $(HOSTCONF)
+	cd $< && $(MAKE) install
+	touch $@