ldmain.c (ld_canon_sysroot, ld_canon_sysroot_len): Define. (main): Initialize them.

ldmain.c (ld_canon_sysroot, ld_canon_sysroot_len): Define. (main): Initialize them.
ldfile.c: Include pathnames.h. (is_sysrooted_pathname): New. (ldfile_add_library_path): Use it.
  (ldfile_open_file_search): Likewise.  Use IS_ABSOLUTE_PATH.
  Don't search_dirs if given an absolute pathname.
  (ldfile_open_file): Issue error message for sysrooted	absolute pathnames.