RFA: Add %T spec file construct for linker scripts

[Nick Clifton]

Hi Guys,

  A customer recently noticed some strange behaviour with default
  linker scripts specified via the LIB_SPEC component of a specs
  file.  If a file in the current directory happens to match the name
  of the linker script selected then this file will be used in
  preference to the actual script.  Eg:

    % m32c-elf-gcc -mcpu=m32c -c foo.c
    % m32c-elf-objdump -ld foo.o > m32c.ld
    % m32c-elf-gcc -mcpu=m32c foo.o
    m32c-elf-ld:m32c.ld:2: syntax error
    collect2: ld returned 1 exit status

  The attached patch fixes this problem by adding support for a new %T
  construct to the spec file syntax.  This acts in a similar way to
  the %s construct, which is currently used for locating linker
  scripts.  There are three differences in its behaviour however:

    * It only scans the library search paths.  It does not search the
      current directory.

    * If the file is found it inserts into the command line being
      constructed with a --script switch prefixed.  (This is for
      convenience - it keeps the spec files simpler).

    * If the file is not found an error message is generated telling
      the user that the script could not be found.

  Tested without regressions on an m32c-elf toolchain and an
  i686-pc-linux-gnu native.

  OK to apply ?

Cheers
  Nick

gcc/ChangeLog
2009-07-14  Nick Clifton  <nickc@redhat.com>

	* gcc.c (this_is_linker_script): New variable.  Like
	this_is_library_file but for the %T constructor.
	(end_going_arg): If this_is_linker_script is set then locate the
	script and insert a --script switch before it
        (do_spec_2): Initialise this_is_linker_script.
        (do_spec_1): Likewise.  Handle %T construct.
        (eval_spec_function): Preserve this_is_linker_script.
	* doc/invoke.texi: Document %T construct in spec files.
	* config/m32c/m32c.h (LIB_SPEC): Use it.

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