awk problem

["Shin'ichiro TAYA" <taya%ba2.so-net.ne.jp@localhost>]

Hi,
I'm trying to make kernel of OPENBLOCKS266.
It needs src/sys/arch/evbppc/compile/walnut-mkimg.sh to convert ELF
kernel to platform specific format.
In the script above, awk uses following expression.

   awk 'BEGIN { printf "\x00\x52\x50\x4f" }

It seems that nawk doesn't support this but gawk does.

   % awk 'BEGIN { printf "\x00\x52\x50\x4f" }' | hexdump -C
   %

   % gawk 'BEGIN { printf "\x00\x52\x50\x4f" }' | hexdump -C
   00000000  00 52 50 4f                                       |.RPO|
   00000004
   %

Is this a problem of nawk ?
Or is this a GNU awk specific extention?