rs6000: Incorporate new builtins code into the build machinery

rs6000: Incorporate new builtins code into the build machinery

2021-07-27  Bill Schmidt  <wschmidt@linux.ibm.com>

gcc/
	* config.gcc (powerpc*-*-*): Add rs6000-builtins.o to extra_objs.
	* config/rs6000/rs6000-gen-builtins.c (main): Close init_file
	last.
	* config/rs6000/t-rs6000 (rs6000-gen-builtins.o): New target.
	(rbtree.o): Likewise.
	(rs6000-gen-builtins): Likewise.
	(rs6000-builtins.c): Likewise.
	(rs6000-builtins.h): Likewise.
	(rs6000.o): Add dependency.
	(EXTRA_HEADERS): Add rs6000-vecdefines.h.
	(rs6000-vecdefines.h): New target.
	(rs6000-builtins.o): Likewise.
	(rs6000-call.o): Add rs6000-builtins.h as a dependency.
	(rs6000-c.o): Likewise.