build.sh continues even if cpio command fails

[detly]

I attempted to build an image from the branch for PR #231 in a debian:bookworm-slim Docker container, and ended up with an initramfs that was 20 bytes:

root@2521e248c037:~/raspberrypi-ua-netinst# stat build_dir/bootfs/raspberrypi-ua-netinst/initramfs.gz 
  File: build_dir/bootfs/raspberrypi-ua-netinst/initramfs.gz
  Size: 20        	Blocks: 8          IO Block: 4096   regular file

This was because cpio was missing, but build.sh happily continued after the point it was needed, despite the set -e that I presume is to prevent exactly such a thing:

 Adding dependency libffi.so.8 => tmp/usr/lib/arm-linux-gnueabihf/libffi.so.8
 Adding dependency libgcc_s.so.1 => tmp/lib/arm-linux-gnueabihf/libgcc_s.so.1
./build.sh: line 463: cpio: command not found
  adding: COPYING.linux (deflated 62%)
  adding: LICENCE.broadcom (deflated 45%)

My understanding is that because the cpio command is in a pipe, its result is considered "used" and any errors from it are thus ignored even with set -e:

(cd rootfs && find . | cpio -H newc -ov | gzip --best > $INITRAMFS)

However, I don't know whether a blanket set -o pipefail would be wise for the whole script (if that is indeed what's required), or whether you need something more precise.