fontconfig's configure looks for <expat.h>

So we need to use the expat subdir too in
--with-expat-includes. Apparently until now it did not find expat.h,
so it fell back to libxml2 instead then, which was sometimes found OK,
sometimes (on tinderboxes) not. (It even went looking in the *build*
platform /usr/include, eek!)

Change-Id: If0595b810d531b5aa7110f375d4d0dfb0b01617b

fontconfig/ExternalProject_fontconfig.mk

@@ -24,7 +24,7 @@ $(call gb_ExternalProject_get_state_target,fontconfig,build) :
 	&& $(if $(debug),CFLAGS=-g) $(if $(filter ANDROID,$(OS)),LIBS="-lm") ./configure \
 		--disable-shared \
 		--with-arch=arm \
-		--with-expat-includes=$(OUTDIR)/inc/external \
+		--with-expat-includes=$(OUTDIR)/inc/external/expat \
 		--with-expat-lib=$(OUTDIR)/lib \
 		--with-freetype-config=$(OUTDIR)/bin/freetype-config \
 		--build=$(BUILD_PLATFORM) --host=$(HOST_PLATFORM) \