configure: support --extra-ldflags

Add --extra-ldflags to configure for static link libaio.

Signed-off-by: Duo LI <[email protected]>

Author: pirDOL

configure

@@ -215,6 +215,8 @@ for opt do
   ;;
   --extra-cflags=*) CFLAGS="$CFLAGS $optarg"
   ;;
+  --extra-ldflags=*) LDFLAGS="$LDFLAGS $optarg"
+  ;;
   --build-32bit-win) build_32bit_win="yes"
   ;;
   --target-win-ver=*) target_win_ver="$optarg"