Build HarfBuzz with CoreText support also for iOS

Change-Id: Id755894def35d59836dff8cff7df1273a8e296b2

external/harfbuzz/ExternalProject_harfbuzz.mk

@@ -37,7 +37,7 @@ $(call gb_ExternalProject_get_state_target,harfbuzz,build) :
 			--with-cairo=no \
 			--with-glib=no \
 			--with-graphite2=yes \
-			$(if $(filter MACOSX,$(OS)),--with-coretext=yes) \
+			$(if $(filter IOS MACOSX,$(OS)),--with-coretext=yes) \
 			$(if $(verbose),--disable-silent-rules,--enable-silent-rules) \
 			$(if $(CROSS_COMPILING),--build=$(BUILD_PLATFORM) --host=$(HOST_PLATFORM)) \
 			CXXFLAGS=' \

external/harfbuzz/UnpackedTarball_harfbuzz.mk

@@ -24,4 +24,8 @@ $(eval $(call gb_UnpackedTarball_add_patches,harfbuzz, \
 ))
 endif
 
+$(eval $(call gb_UnpackedTarball_add_patches,harfbuzz, \
+    external/harfbuzz/harfbuzz-ios.patch \
+))
+
 # vim: set noet sw=4 ts=4:

external/harfbuzz/harfbuzz-ios.patch

@@ -0,0 +1,11 @@
+--- configure
++++ configure
+@@ -19046,6 +19046,8 @@
+ 
+ 	else
+ 		# On iOS CoreText and CoreGraphics are stand-alone frameworks
++               # Forget the cache failure to find CTFontRef above
++               unset ac_cv_type_CTFontRef
+ 		if test "x$have_coretext" != "xtrue"; then
+ 			ac_fn_c_check_type "$LINENO" "CTFontRef" "ac_cv_type_CTFontRef" "#include <CoreText/CoreText.h>
+ "