Add HB_NO_OEPN (#1767)

src/hb-blob.cc

@@ -543,6 +543,9 @@ _hb_mapped_file_destroy (void *file_)
 hb_blob_t *
 hb_blob_create_from_file (const char *file_name)
 {
+#ifdef HB_NO_OEPN
+  return hb_blob_get_empty ();
+#endif
   /* Adopted from glib's gmappedfile.c with Matthias Clasen and
      Allison Lortie permission but changed a lot to suit our need. */
 #if defined(HAVE_MMAP) && !defined(HB_NO_MMAP)

src/hb-config.hh

@@ -60,7 +60,9 @@
 #define HB_NO_GETENV
 #define HB_NO_LAYOUT_UNUSED
 #define HB_NO_MATH
+#define HB_NO_MMAP
 #define HB_NO_NAME
+#define HB_NO_OEPN
 #define HB_NO_SETLOCALE
 #define HB_NO_SUBSET_LAYOUT
 #endif