[amalgam] Use it in cmake port and fix conflicts (#1812)

src/hb-coretext.cc

diff --git a/src/hb-coretext.cc b/src/hb-coretext.cc
index a57b970..e8a4fd5 100644
--- a/src/hb-coretext.cc
+++ b/src/hb-coretext.cc
@@ -75,7 +75,7 @@
 }
 
 static hb_blob_t *
-reference_table  (hb_face_t *face HB_UNUSED, hb_tag_t tag, void *user_data)
+_hb_cg_reference_table (hb_face_t *face HB_UNUSED, hb_tag_t tag, void *user_data)
 {
   CGFontRef cg_font = reinterpret_cast<CGFontRef> (user_data);
   CFDataRef cf_data = CGFontCopyTableForTag (cg_font, tag);
@@ -299,7 +299,7 @@
 hb_face_t *
 hb_coretext_face_create (CGFontRef cg_font)
 {
-  return hb_face_create_for_tables (reference_table, CGFontRetain (cg_font), _hb_cg_font_release);
+  return hb_face_create_for_tables (_hb_cg_reference_table, CGFontRetain (cg_font), _hb_cg_font_release);
 }
 
 /*