Additional --with-build-sysroot tweak

[Mark Mitchell]

For GNU/Linux targets, it turns out that we need the following
additional change at the topelvel.  What config/mt-gnu wants to say
is:

  CXXFLAGS_FOR_TARGET += -D_GNU_SOURCE

but that's GNU-makeful.  So, it's copied the top-level defaults; now
that the defaults have changed, that needs to be propogated here.

OK?

--
Mark Mitchell
CodeSourcery, LLC
mark@codesourcery.com

2005-07-27  Mark Mitchell  <mark@codesourcery.com>

	* config/mt-gnu (CXXFLAGS): Include SYSROOT_CFLAGS_FOR_TARGET.

*** config/mt-gnu	22 May 2001 01:17:23 -0000	1.4
--- config/mt-gnu	27 Jul 2005 14:42:12 -0000
***************
*** 1 ****
! CXXFLAGS_FOR_TARGET = $(CXXFLAGS) -D_GNU_SOURCE
--- 1 ----
! CXXFLAGS_FOR_TARGET = $(CXXFLAGS) $(SYSROOT_CFLAGS_FOR_TARGET) -D_GNU_SOURCE