Darwin, configury : Allow for specification and detection of dsymutil.

Darwin, configury : Allow for specification and detection of dsymutil.

In order to enable DWARF versions > 2 we need a sufficiently modern
version of dsymutil (in addition to the assembler / linker).  This
allows the user to configure a different path from the installed one.

In addition, there are several sources of dsymutil so we differentiate
these in order to be get accurate version information.

Backported from commits 3b5e8ee4f1ecc6d407f391695f65960bcbd63cff and
b019b28ebd65462a092c96d95e9e356c8bb39b78

Signed-off-by: Iain Sandoe <iain@sandoe.co.uk>
gcc/ChangeLog:

	* configure.ac: Handle --with-dsymutil in the same way as we
	do for the assembler and linker.  (DEFAULT_DSYMUTIL): New.
	Extract the type and version for the dsymutil configured or
	found by the default searches.
	* config.in: Regenerated.
	* configure: Regenerated.
	* collect2.c (do_dsymutil): Handle locating dsymutil in the
	same way as for the assembler and  linker.
	* config/darwin.h (DSYMUTIL): Delete.
	* gcc.c: Report a configured dsymutil correctly.
	* exec-tool.in: Allow for dsymutil.
	* doc/install.texi: Document --with-dsymutil.

ChangeLog:

	* Makefile.def: Add dsymutil defs.
	* Makefile.in: Regenerated.
	* Makefile.tpl: Add dsymutil to flags.
	* configure: Regenerated.
	* configure.ac: Add dsymutil to target and build recipes.