configure: move config.fate creation after OS section

The OS label can be changed, and we want this to be reflected.

Originally committed as revision 24953 to svn://svn.ffmpeg.org/ffmpeg/trunk

configure

@@ -2231,8 +2231,6 @@ esac
 enable $subarch
 enabled spic && enable pic
 
-echo "config:$arch:$subarch:$cpu:$target_os:$cc_ident:$FFMPEG_CONFIGURATION" >config.fate
-
 # OS specific
 case $target_os in
     haiku)
@@ -2380,6 +2378,8 @@ case $target_os in
         ;;
 esac
 
+echo "config:$arch:$subarch:$cpu:$target_os:$cc_ident:$FFMPEG_CONFIGURATION" >config.fate
+
 check_cpp_condition stdlib.h "defined(__PIC__) || defined(__pic__) || defined(PIC)" && enable pic
 
 set_default $PATHS_LIST