Declare these without `static', to avoid warning that we haven't
defined them.
* Makerules (build-module-helper-objlist): New variable,
broken out of build-module. Insert --whole-archive/--no-whole-archive
immediately each *_pic.a file in the link object list.
(whole-archive): New variable, used by that.
(build-module-objlist): New variable using build-module-helper-objlist.
(build-module, build-module-helper): Use it.
(build-shlib-objlist): New variable using build-module-helper-objlist.
(build-shlib): Use that.
* sysdeps/mach/hurd/Makefile ($(link-rpcuserlibs)): Likewise.