[config] Add HB_NO_LAYOUT_COLLECT_GLYPHS

Part of
diff --git a/src/hb-config.hh b/src/hb-config.hh
index 74e4ef5..66af29a 100644
--- a/src/hb-config.hh
+++ b/src/hb-config.hh
@@ -62,6 +62,7 @@
 #define HB_NO_HINTING
 #define HB_NO_LANGUAGE_PRIVATE_SUBTAG
 #define HB_NO_LAYOUT_FEATURE_PARAMS
+#define HB_NO_LAYOUT_COLLECT_GLYPHS
 #define HB_NO_LAYOUT_UNUSED
 #define HB_NO_MATH
 #define HB_NO_MMAP
diff --git a/src/hb-ot-layout.cc b/src/hb-ot-layout.cc
index 0b897d5..10b9ba0 100644
--- a/src/hb-ot-layout.cc
+++ b/src/hb-ot-layout.cc
@@ -1203,6 +1203,7 @@
 }
 
 
+#ifndef HB_NO_LAYOUT_COLLECT_GLYPHS
 /**
  * hb_ot_layout_lookup_collect_glyphs:
  * @face: #hb_face_t to work upon
@@ -1249,6 +1250,7 @@
     }
   }
 }
+#endif
 
 
 /* Variations support */