gcc.c: Add linker spec.

gcc.c: Add linker spec.

        * gcc.c: Add linker spec.
        (link_command_spec): Use %(linker) instead of ld.
        (main): If collect2 is requested as the linker, see if it exists;
        if not, use ld instead.
        * Makefile.in (USE_COLLECT2): It's named collect2 now, not ld.
        (ld:) Deleted.
        (install-collect2): Install as collect2, not ld.
        * configure.in(will_use_collect2): It's named collect2 now.
        * collect2: Remove checks to see if we were invoked recursively.
        (collect_execute): Use _spawnvp under cygwin32.

From-SVN: r19022