Fail if format.lds comes out empty.

ChangeLog

@@ -1,5 +1,7 @@
 2011-07-02  Roland McGrath  <roland@hack.frob.com>
 
+	* Makerules ($(common-objpfx)format.lds): Fail if result is empty.
+
 	* Makefile ($(common-objpfx)testrun.sh): Generate to work relative to
 	containing directory rather than embedding absolute directory names.
 

Makerules

@@ -993,6 +993,7 @@ $(common-objpfx)format.lds: $(..)scripts/output-format.sed \
 	$(LINK.o) -shared $(sysdep-LDFLAGS) $(config-LDFLAGS) $(LDFLAGS.so) \
 		  -x c /dev/null -o $@.so -Wl,--verbose -v 2>&1 \
 	| sed -n -f $< > $@.new
+	test -s $@.new
 	rm -f $@.so
 	mv -f $@.new $@
 common-generated += format.lds