Do not attempt installing reform-qcacld2 in the background if inside chroot

If this script is not run on a real system with a real init process but
in a container-like chroot environment, then creating these background
processes without waiting for their completion will leave zombie
processes behind which hog resources like /dev/null and thus prevent the
container software from cleanly un-mounting bind-mounts as they may have
been created for /dev/null. We cannot reliably detect whether the
container manager will automatically wait for and reap zombie processes,
so as a hacky workaround, we just make this script a no-op if it is
started inside a chroot environment.

debian-meta/etc/kernel/postinst.d/reform-qcacld2

@@ -14,6 +14,20 @@ update_package() {
   apt install -y reform-qcacld2
 }
 
+# If this script is not run on a real system with a real init process
+# but in a container-like chroot environment, then creating these
+# background processes without waiting for their completion will leave
+# zombie processes behind which hog resources like /dev/null and thus
+# prevent the container software from cleanly un-mounting bind-mounts
+# as they may have been created for /dev/null. We cannot reliably
+# detect whether the container manager will automatically wait for and
+# reap zombie processes, so as a hacky workaround, we just make this
+# script a no-op if it is started inside a chroot environment
+if ischroot; then
+	echo "I: chroot environment detected: not attempting to install reform-qcacld2 in the background" >&2
+	exit 0
+fi
+
 echo "Starting background process to update reform-qcacld2 driver package (for Wi-Fi) to match kernel version."
 
 # Background because we need to wait for the main running apt install process to finish