build: more correct build rules for build/gen% programs.

build: more correct build rules for build/gen% programs.

gcc/:
	PR bootstrap/45796
	* Makefile.in (build/gen%$(build_exeext)): Move rule after all
	special-casing for generators and turn into ...
	((genprog:%=build/gen%$(build_exeext))): ... this static pattern
	rule, for better error messages in case of toplevel dependency
	errors.
	(genprog): Add hooks, rename to ...
	(genprogerr): ... this, and let genprog also contain check,
	checksum, condmd.
	((genprog:%=build/gen%$(build_exeext))): Rename to ...
	((genprogerr:%=build/gen%$(build_exeext))): ... this.
	(build/genhooks$(build_exeext)): Remove now-unneeded dependency.

From-SVN: r164759