Ada: Fix s-oscons.ads generation

The $(GNATLIBCFLAGS) are already included in $(GNATLIBCFLAGS_FOR_C).

We must call the C compiler with the right machine flags.  So, add
$(GNATLIBCFLAGS_FOR_C) to $(OSCONS_EXTRACT).  For example, on a bi-arch
compiler supporting 32-bit and 64-bit instruction sets we pick otherwise
only one variant due to a missing -m32 or -m64 flag.

gcc/ada
	* gcc-interface/Makefile.in (OSCONS_CPP): Remove redundant
	$(GNATLIBCFLAGS).
	(OSCONS_EXTRACT): Add $(GNATLIBCFLAGS_FOR_C).

From-SVN: r258334

gcc/ada/ChangeLog

+2018-03-07  Sebastian Huber  <sebastian.huber@embedded-brains.de>
+
+	* gcc-interface/Makefile.in (OSCONS_CPP): Remove redundant
+	$(GNATLIBCFLAGS).
+	(OSCONS_EXTRACT): Add $(GNATLIBCFLAGS_FOR_C).
+
 2018-03-06  Eric Botcazou  <ebotcazou@adacore.com>
 
 	* gcc-interface/trans.c (convert_with_check): Fix typo in the condition

gcc/ada/gcc-interface/Makefile.in

@@ -2381,9 +2381,9 @@ OSCONS_CC=$(subst ./xgcc,../../xgcc,$(subst -B./, -B../../,$(GCC_FOR_TARGET)))
 # ada/types.h does not conflict with a same-named system header (VxWorks
 # has a <types.h> header).
 
-OSCONS_CPP=$(OSCONS_CC) $(GNATLIBCFLAGS) $(GNATLIBCFLAGS_FOR_C) -E -C \
+OSCONS_CPP=$(OSCONS_CC) $(GNATLIBCFLAGS_FOR_C) -E -C \
   -DTARGET=\"$(target)\" -iquote $(fsrcpfx)ada $(fsrcpfx)ada/s-oscons-tmplt.c > s-oscons-tmplt.i
-OSCONS_EXTRACT=$(OSCONS_CC) -S s-oscons-tmplt.i
+OSCONS_EXTRACT=$(OSCONS_CC) $(GNATLIBCFLAGS_FOR_C) -S s-oscons-tmplt.i
 
 # Note: if you need to build with a non-GNU compiler, you could adapt the
 # following definitions (written for VMS DEC-C)