ELF/BFD: Limit `_bfd_elf_link_renumber_dynsyms' call in section GC
    
    Consistently call `_bfd_elf_link_renumber_dynsyms' only if linking a
    dynamic binary, complementing code in `bfd_elf_size_dynsym_hash_dynstr'
    and commit ccabcbe51e85 ("New attempt at fixing MIPS --gc-sections et
    al."), <https://sourceware.org/ml/binutils/2005-08/msg00258.html>.
    
    	bfd/
    	* elflink.c (elf_gc_sweep): Only call
    	`_bfd_elf_link_renumber_dynsyms' if dynamic sections have been
    	created.
    
    (backported from commit c46cec3a8cfe02fbe0f6c67ba53abc5369c5c659)