Don't include subset headers in libharfbuzz.
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 6199e44..27a04b1 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -267,7 +267,6 @@
 
   ${HB_BASE_headers}
   ${HB_OT_headers}
-  ${HB_SUBSET_headers}
 )
 
 set (subset_project_headers