[config] Add HB_NO_GDEF_CACHE

src/OT/Layout/GDEF/GDEF.hh

diff --git a/src/OT/Layout/GDEF/GDEF.hh b/src/OT/Layout/GDEF/GDEF.hh
index 95d7a71..c1ff796 100644
--- a/src/OT/Layout/GDEF/GDEF.hh
+++ b/src/OT/Layout/GDEF/GDEF.hh
@@ -865,18 +865,27 @@
     unsigned int get_glyph_props (hb_codepoint_t glyph) const
     {
       unsigned v;
+
+#ifndef HB_NO_GDEF_CACHE
       if (glyph_props_cache.get (glyph, &v))
         return v;
+#endif
 
       v = table->get_glyph_props (glyph);
+
+#ifndef HB_NO_GDEF_CACHE
       if (likely (table.get_blob ())) // Don't try setting if we are the null instance!
 	glyph_props_cache.set (glyph, v);
+#endif
 
       return v;
+
     }
 
     hb_blob_ptr_t<GDEF> table;
+#ifndef HB_NO_GDEF_CACHE
     mutable hb_cache_t<21, 3, 8> glyph_props_cache;
+#endif
   };
 
   void collect_variation_indices (hb_collect_variation_indices_context_t *c) const

src/hb-config.hh

diff --git a/src/hb-config.hh b/src/hb-config.hh
index 22587f6..1ed39bb 100644
--- a/src/hb-config.hh
+++ b/src/hb-config.hh
@@ -189,6 +189,7 @@
 
 #ifdef HB_OPTIMIZE_SIZE
 #define HB_NO_OT_LAYOUT_LOOKUP_CACHE
+#define HB_NO_GDEF_CACHE
 #endif