For relative paths in INPUT() and GROUP(), search the directory of the current linker script before searching other paths.

PR ld/25806
	* ldlang.h (struct lang_input_statement_struct): Add extra_search_path.
	* ldlang.c (current_input_file): New.
	(ldirname): New.
	(new_afile): Add from_filename parameter. Set extra_search_path.
	(lang_add_input_file): Pass current_input_file to new_afile.
	(load_symbols): Set current_input_file.

ld/ldlang.h

@@ -293,6 +293,9 @@ typedef struct lang_input_statement_struct
      Usually the same as filename, but for a file spec'd with
      -l this is the -l switch itself rather than the filename.  */
   const char *local_sym_name;
+  /* Extra search path. Used to find a file relative to the
+     directory of the current linker script.  */
+  const char *extra_search_path;
 
   bfd *the_bfd;