configure: use AS_O setting in check_as

Signed-off-by: Mans Rullgard <mans@mansr.com>

configure

@@ -652,11 +652,15 @@ check_cpp(){
     check_cmd $cc $CPPFLAGS $CFLAGS "$@" $(cc_e $TMPO) $TMPC
 }
 
+as_o(){
+    eval printf '%s\\n' $AS_O
+}
+
 check_as(){
     log check_as "$@"
     cat > $TMPC
     log_file $TMPC
-    check_cmd $as $CPPFLAGS $ASFLAGS "$@" $AS_C -o $TMPO $TMPC
+    check_cmd $as $CPPFLAGS $ASFLAGS "$@" $AS_C $(as_o $TMPO) $TMPC
 }
 
 check_inline_asm(){