Add rdynamic-1 test

It is added for

commit 409ff343a402799563f71f938138b29f8baf7a1c
Author: Alan Modra <amodra@gmail.com>
Date:   Tue Nov 8 13:49:11 2011 +0000

      * elflink.c (bfd_elf_gc_mark_dynamic_ref_symbol): Mark syms in
      executables when export_dynamic.

	* ld-elf/rdynamic-1.c: New file.
	* ld-elf/rdynamic-1.rd: Likewise.

	* ld-elf/shared.exp (build_tests): Add rdynamic-1.
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