(main): Look for `real-ld' after `gld', before `ld'.

(main): Look for `real-ld' after `gld', before `ld'.

Fix typo in -debug part of previous change.

Look for tools using paths rather than a single prefix.
(struct prefix_list, struct path_prefix): New structures.
(cpath, path): New variables.
(find_a_file, add_prefix): New functions; simplified versions of
functions from gcc.c.
(prefix_from_env): New function.
(main): Get path to search for binaries from COMPILER_PATH
environment variable always set by gcc.c and from PATH.
Qualify names with target machine in cross-environment unless
using compiler directories.
Use find_a_file to find our binaries.
Remove use of single prefix.
If -debug, print strip_file_name.
(fork_execute): Print program we are trying to execute if -debug and
we can't find the file.
(scan_prog_file): Complain if can't find nm.

From-SVN: r3052