`--mount` option problem for building Postgres image

Expected Behavior

Running pgbench benchmark on PostgreSQL as a probe should be enough for docker-slim to create a minified image which can handle same load. Creating a database, filling it with some data and running some concurrent queries is what pgbench do.

Actual Behavior

But after building slim image some odd behavior appear:

• Postgres image (specially on alpine) isn't minified.
• docker-slim doesn't respect --mount and --exclude-mounts, generated image still has files in mounted volume location.
• Some log showing artifact sensor facing don't exist problem and missing in rawNames

Steps to Reproduce the Problem

docker-slim build \
    --target postgres:14.3-alpine \
    --env POSTGRES_HOST_AUTH_METHOD=trust \
    --show-clogs=true \
    --http-probe=false \
    --mount pgdata:/var/lib/postgresql/data/ \
    --exclude-mounts \
    --exec "pgbench -i -U postgres -s 10 postgres && pgbench -U postgres -c 10 -t 2000 postgres && psql -U postgres postgres -c 'DROP TABLE pgbench_accounts, pgbench_branches, pgbench_tellers, pgbench_history;'"

log file is attached.

for testing minified image run this docker-compose:

version: '3.3'
services:
  postgres:
    image: postgres.slim:latest
    environment:
      POSTGRES_HOST_AUTH_METHOD: trust
  tester:
    image: postgres:14.3
    entrypoint:
      - bash
      - -c
      - "sleep 3; pgbench -i -U postgres -h postgres -s 50 postgres && pgbench -U postgres -h postgres -c 30 -t 10000 postgres"

Postgres exits with this error:

PostgreSQL Database directory appears to contain a database; Skipping initialization
FATAL:  58P01: could not open directory "/usr/local/lib/postgresql": No such file or directory

Specifications

• Version: docker-slim version linux|Transformer|1.37.6|26a36c88a94c677efd734e874ba081dabb84a224|2022-04-23_06:03:56AM
• Platform: Ubuntu 18.04.6 LTS, docker-slim ran on host (not in a container)

Start by reproducing the issue with the provided docker-slim build command and inspect the attached postgres.log, focusing on --mount, --exclude-mounts, and the artifact sensor messages. Done means the PostgreSQL image is minified, mounted-volume files are excluded, and the resulting image can run the supplied pgbench docker-compose workload without the missing-directory error.