util/chromeos/gen_test_hwid.sh: Replace usage of hexdump

Hexdump command is not available in coreboot-sdk. Replace it with
equivalent implementation using commands that are present in the
container.

TEST=Passed "VP46XX" as prefix variable and it produced the same
crc32 result before and after the change.

Signed-off-by: Michał Żygowski <michal.zygowski@3mdeb.com>
Change-Id: Icad93933335b8c5ebd8fee74cc9aaed36bb56482
Reviewed-on: https://review.coreboot.org/c/coreboot/+/68133
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Julius Werner <jwerner@chromium.org>

util/chromeos/gen_test_hwid.sh

@@ -13,7 +13,7 @@ main() {
   local prefix="$(echo "${board}" | tr a-z A-Z) TEST"
   # gzip has second-to-last 4 bytes in CRC32.
   local crc32="$(printf "${prefix}" | gzip -1 | tail -c 8 | head -c 4 | \
-		 hexdump -e '1/4 "%04u" ""' | tail -c 4)"
+		 od -An -vtu4 | tr -d '\n' | tail -c 4)"
 
   echo "${prefix}" "${crc32}"
 }