fix: avoid running cachedir mount commands via script

[egibs]

We currently run all QEMU commands via script when running tests which does not work for the cache directory mount commands:

2025/07/07 16:46:49 INFO qemu: setting up melange cachedir: /tmp/melange-cache
2025/07/07 16:46:49 WARN ash: script: not found
2025/07/07 16:46:49 ERRO Failed to run command "script -f -q --log-in /dev/null --log-out /dev/null -e -c 'sh -c '\\''mkdir -p /var/cache/melange /mount/var/cache/melange /mount/upper /mount/work && mount -t 9p melange_cache /var/cache/melange && mount -t overlay overlay -o lowerdir=/var/cache/melange,upperdir=/mount/upper,workdir=/mount/work /mount/var/cache/melange'\\'": Process exited with status 127

This PR avoids running the initial StartPod commands via script while leaving all of the test pipelines unaltered.

That said, script is now causing certain test commands to hang, so we'll have to follow up on that in a separate PR.

[stevebeattie]

I think this is the right approach, but it seems possible in the future that we'd have potentially other setup commands to run outside of the chroot environment under /mount -- I wonder if it'd be better to have either an argument to the function or variant of it that is for environment setup that causes the injection of the script ... bits to be avoided, rather than specifically hard-coding it for the overlay mount command.

[egibs]

I think this is the right approach, but it seems possible in the future that we'd have potentially other setup commands to run outside of the chroot environment under /mount -- I wonder if it'd be better to have either an argument to the function or variant of it that is for environment setup that causes the injection of the script ... bits to be avoided, rather than specifically hard-coding it for the overlay mount command.

2d4719d (#2070) is a better attempt that only sets TestRun at the pipeline level after we run StartPod.

e.g.,

cmd: sh -c 'mkdir -p /var/cache/melange /mount/var/cache/melange /mount/upper /mount/work && mount -t 9p melange_cache /var/cache/melange && mount -t overlay overlay -o lowerdir=/var/cache/melange,upperdir=/mount/upper,workdir=/mount/work /mount/var/cache/melange' test run: false
2025/07/07 19:05:58 INFO qemu: setting up local workspace
cmd: sh -c 'find /mnt/ -mindepth 1 -maxdepth 1 -exec cp -a {} /home/build/ \;' test run: false                                                                        2025/07/07 19:05:58 INFO running the main test pipeline
cmd: /bin/sh -c 'set -ex
[ -d '\''/home/build'\'' ] || mkdir -p '\''/home/build'\''
cd '\''/home/build'\''
find / -name "script"                                                                                                                                                   cd "${ZK_HOME}"
cp conf/zoo_sample.cfg conf/zoo.cfg
bin/zkServer.sh start-foreground &                                                                                                                                      ZOOKEEPER_PID=$!
bin/zkCli.sh | grep "Welcome to ZooKeeper!"
bin/zkCli.sh create /test-$(uuidgen) '\''$(uuidgen)'\''                                                                                                                 kill "${ZOOKEEPER_PID}"

exit 0' test run: true