configure: redirect -fsplit-stack compilation to dev/null
    
    Avoid an error message in the middle of the configure output.
    
    Patch by Eric Botcazou.
    
    Reviewed-on: https://go-review.googlesource.com/30813

From-SVN: r240993
diff --git a/libgo/configure.ac b/libgo/configure.ac
index 0f98ae8..e721b0f 100644
--- a/libgo/configure.ac
+++ b/libgo/configure.ac
@@ -447,9 +447,9 @@
 cat > conftest2.c << EOF
 void f() {}
 EOF
-$CC -c -fsplit-stack $CFLAGS $CPPFLAGS conftest1.c
-$CC -c $CFLAGS $CPPFLAGS conftest2.c
-if $CC -o conftest conftest1.$ac_objext conftest2.$ac_objext; then
+$CC -c -fsplit-stack $CFLAGS $CPPFLAGS conftest1.c >/dev/null 2>&1
+$CC -c $CFLAGS $CPPFLAGS conftest2.c > /dev/null 2>&1
+if $CC -o conftest conftest1.$ac_objext conftest2.$ac_objext > /dev/null 2>&1; then
   libgo_cv_c_linker_split_non_split=yes
 else
   libgo_cv_c_linker_split_non_split=no