Fix building of cross compiler (PR target/81753).

2017-08-16  Martin Liska  <mliska@suse.cz>

	PR target/81753
	* config.gcc: Respect previously set extra_objs in case
	of darwin target.

From-SVN: r251118

gcc/ChangeLog

+2017-08-16  Martin Liska  <mliska@suse.cz>
+
+	PR target/81753
+	* config.gcc: Respect previously set extra_objs in case
+	of darwin target.
+
 2017-08-16  Richard Sandiford  <richard.sandiford@linaro.org>
 
 	PR tree-optimization/81835

gcc/config.gcc

@@ -653,7 +653,7 @@ case ${target} in
   cxx_target_objs="${cxx_target_objs} darwin-c.o"
   fortran_target_objs="darwin-f.o"
   target_has_targetcm=yes
-  extra_objs="darwin.o"
+  extra_objs="${extra_objs} darwin.o"
   extra_gcc_objs="darwin-driver.o"
   default_use_cxa_atexit=yes
   use_gcc_stdint=wrap