configure.ac: Do not create links, only substitute the filenames.

configure.ac: Do not create links, only substitute the filenames.

	* configure.ac: Do not create links, only substitute the filenames.
	* configure: Regenerate.
	* Makefile.in: Assign the substitution results to variables.
	(LIBGCC_LINKS): Define.
	(enable-execute-stack.c): New rule.
	(unwind.h): Likewise.
	(md-unwind-support.h): Likewise.
	(sfp-machine.h): Likewise.
	(gthr-default.h): Likewise.
	Add $(LIBGCC_LINKS) to the prerequisites of all object files and
	unwind.h as prerequisite of install-unwind_h-forbuild.

From-SVN: r240312