[config] Disable hb-ot-font code if HB_NO_OT_FONT

Part of https://github.com/harfbuzz/harfbuzz/issues/1652

src/hb-ot-font.cc

diff --git a/src/hb-ot-font.cc b/src/hb-ot-font.cc
index 0707a2f..5895c7b 100644
--- a/src/hb-ot-font.cc
+++ b/src/hb-ot-font.cc
@@ -26,6 +26,8 @@
 
 #include "hb.hh"
 
+#ifndef HB_NO_OT_FONT
+
 #include "hb-ot.h"
 
 #include "hb-font.hh"
@@ -317,3 +319,6 @@
 		     &font->face->table,
 		     nullptr);
 }
+
+
+#endif