Add --remap-inputs option to the BFD linker.

  PR 30374
  * ldfile.c (struct input_remap): New structure. (ldfile_add_remap): New function. (ldfile_remap_input_free): New function. (ldfile_add_remap_file): New function. (ldfile_possibly_remap_input): New function. (ldfile_print_input_remaps): New function. * ldfile.h: Add prototypes for new functions.
  * ldlang.c (new_afile): Call ldfile_possibly_remap_input. (lang_finish): Call ldfile_remap_input_free. (lang_map): Call ldfile_print_input_remaps.
  * ldlex.h (OPTION_REMAP_INPUTS, OPTION_REMAP_INPUTS_FILE): Define.
  * lexsup.c (ld_options): Add --remap-inputs-file and --remap-inputs. (parse_args): Handle new options.
  * NEWS: Mention the new feature.
  * ld.texi: Document the new options.
  * testsuite/ld-misc/input-remap.exp: New test driver.
  * testsuite/ld-misc/remaps.r: New file: Expected linker output.
  * testsuite/ld-misc/remaps.txt: New file.  Input remaps file.