fix: use POSIX sh and add EXIT trap in entrypoint

Signed-off-by: danbugs <danilochiarlone@gmail.com>

Author: danbugs

host/pyhl-entrypoint.sh

@@ -1,13 +1,13 @@
-#!/bin/bash
+#!/bin/sh
 set -e
 
 if [ ! -f "$PYHL_HOME/snapshot/index.json" ]; then
     staging=$(mktemp -d)
+    trap 'rm -rf "$staging"' EXIT
     mkdir -p "$staging/.unikraft/build"
     ln -s "$PYHL_HOME/kernel" "$staging/.unikraft/build/driver_hyperlight-x86_64"
     ln -s "$PYHL_HOME/initrd.cpio" "$staging/driver-initrd.cpio"
     pyhl setup --dest "$PYHL_HOME" --from "$staging" --net --force
-    rm -rf "$staging"
 fi
 
 if [ "$1" = "--setup-only" ]; then