Improve port to platforms lacking euidaccess (Bug#35406)
* lib-src/emacsclient.c (set_local_socket): Use faccessat with AT_EACCESS instead of using euidaccess. * admin/merge-gnulib, lib/gnulib.mk.in, m4/gnulib-comp.m4: Revert previous change.
* lib-src/emacsclient.c (set_local_socket): Use faccessat with AT_EACCESS instead of using euidaccess. * admin/merge-gnulib, lib/gnulib.mk.in, m4/gnulib-comp.m4: Revert previous change.