Вызываем справку:
docker run --rm -v ${PWD}/:/var/task -u 0 node:15-alpine sh --help
BusyBox v1.31.1 () multi-call binary.
Usage: sh [-/+OPTIONS] [-/+o OPT]... [-c 'SCRIPT' [ARG0 [ARGS]] / FILE [ARGS] / -s [ARGS]]
Unix shell interpreter
Таким образом:
docker run --rm -v ${PWD}/:/var/task -u 0 node:15-alpine sh -c "cd /var/task && npm install && npm ci"
А можно и так:
docker run --rm -v ${PWD}/:/var/task -u 0 --workdir="/var/task" node:15-alpine sh -c "npm install && npm ci
Или вообще так:
docker run --rm -v ${PWD}/:/var/task -u 0 --workdir="/var/task" node:15-alpine npm install && npm ci
PS
https://docs.docker.com/engine/reference/run/