[subset] Remove HB_SUBSET_BUILTIN

Just include hb-static.cc in libharfbuzz-subset.so source list as
well.  Those building it built-in will include hb-static.cc once
already.  No need for any gymnastics.

src/Makefile.sources

@@ -203,6 +203,7 @@ HB_ICU_headers = hb-icu.h
 
 # Sources for libharfbuzz-subset
 HB_SUBSET_sources = \
+	hb-static.cc \
 	hb-subset.cc \
 	hb-subset-glyf.cc \
 	hb-subset-input.cc \

src/hb-subset.cc

@@ -44,11 +44,6 @@
 #include "hb-ot-post-table.hh"
 
 
-#if !defined(HB_SUBSET_BUILTIN)
-#include "hb-static.cc"
-#endif
-
-
 struct hb_subset_profile_t {
   hb_object_header_t header;
   ASSERT_POD ();