Avoid warning: 'inflateValidate' is only available on macOS 10.13 or newer

Change-Id: I0f828239ed5aff164ba1f4e486017db0e6c93a4a

external/libpng/UnpackedTarball_libpng.mk

@@ -15,4 +15,8 @@ $(eval $(call gb_UnpackedTarball_add_files,libpng,.,\
 	external/libpng/configs/pnglibconf.h \
 ))
 
+$(eval $(call gb_UnpackedTarball_add_patches,libpng,\
+	external/libpng/libpng-osx.patch.1 \
+))
+
 # vim: set noet sw=4 ts=4:

external/libpng/libpng-osx.patch.1

+-*- Mode: Diff -*-
+
+Avoid warning: 'inflateValidate' is only available on macOS 10.13 or newer [-Wunguarded-availability-new]
+
+--- a/pngrutil.c
++++ b/pngrutil.c
+@@ -419,7 +419,8 @@
+       }
+ 
+ #if ZLIB_VERNUM >= 0x1290 && \
+-   defined(PNG_SET_OPTION_SUPPORTED) && defined(PNG_IGNORE_ADLER32)
++   defined(PNG_SET_OPTION_SUPPORTED) && defined(PNG_IGNORE_ADLER32) && \
++   !(defined(MAC_OS_X_VERSION_MIN_REQUIRED) && MAC_OS_X_VERSION_MIN_REQUIRED < 101300)
+       if (((png_ptr->options >> PNG_IGNORE_ADLER32) & 3) == PNG_OPTION_ON)
+          /* Turn off validation of the ADLER32 checksum in IDAT chunks */
+          ret = inflateValidate(&png_ptr->zstream, 0);