cloud build does not recognize build directory argument

I am trying to build a Cloud Run job with a trigger from Cloud Build and secrets from Secret Manager. I managed to get the trigger that I use to build my Dockerfile to run, but the build itself fails with the following error:

BUILD
Starting Step #0 - "build image"
Step #0 - "build image": Already have image (with digest): gcr.io/cloud-builders/docker
Step #0 - "build image": "docker build" requires exactly 1 argument.
Step #0 - "build image": See 'docker build --help'.
Step #0 - "build image": 
Step #0 - "build image": Usage:  docker build [OPTIONS] PATH | URL | -
Step #0 - "build image": 
Step #0 - "build image": Build an image from a Dockerfile
Finished Step #0 - "build image"
ERROR
ERROR: build step 0 "gcr.io/cloud-builders/docker" failed: step exited with non-zero status: 1

What I have already tried:

1. Verified that there is a build directory in the command;
2. Rearranged the order of build arguments just in case;
3. I also tried breakout syntax (with '|' as one of the arguments), but it did not work out - the image was not built at all.
4. UPDATED: I tried running the build without --build-args and it started actually building! Looks like a bug. Here is my cloudbuild.yaml:

steps:
  - id: "build image"
    name: "gcr.io/cloud-builders/docker"
    entrypoint: 'bash'
    args:
      ['-c', 'docker build --build-arg CONTAINER_PRIVATE_KEY=$$PRIVATE_KEY --build-arg CONTAINER_PUBLIC_KEY=$$PUBLIC_KEY -t gcr.io/${PROJECT_ID}/${_JOB_NAME} .']
    secretEnv: [ 'PRIVATE_KEY', 'PUBLIC_KEY' ]
  - id: "push image"
    name: "gcr.io/cloud-builders/docker"
    args: [ "push", "gcr.io/${PROJECT_ID}/${_JOB_NAME}" ]

  - id: "deploy to cloud run"
    name: 'gcr.io/google.com/cloudsdktool/cloud-sdk'
    entrypoint: gcloud
    args:
            [
              'beta', 'run', '${_JOB_NAME}',
              '--image', 'gcr.io/${PROJECT_ID}/${_JOB_NAME}',
              '--region', '${_REGION}',
              '--set-env-vars', "BUCKET=${_BUCKET}",
              '--set-env-vars', "MNT_DIR=${_MNT_DIR}"
            ]
images:
    - "gcr.io/${PROJECT_ID}/${_JOB_NAME}"
availableSecrets:
  secretManager:
    - versionName: "projects/${_PROJECT_ID_NUMBER}/secrets/${_CONTAINER_PRIVATE_KEY_SECRET_NAME}/versions/latest"
      env: "PRIVATE_KEY"
    - versionName: "projects/${_PROJECT_ID_NUMBER}/secrets/${_CONTAINER_PUBLIC_KEY_SECRET_NAME}/versions/latest"
      env: "PUBLIC_KEY"

So, after extensive testing and trying out various options I have managed to figure out what was causing the issue, below is the correct argument string (it goes in the args):

["-c", "docker build --build-arg 'CONTAINER_PRIVATE_KEY=$$PRIVATE_KEY' --build-arg 'CONTAINER_PUBLIC_KEY=$$PUBLIC_KEY' -t gcr.io/${PROJECT_ID}/${_JOB_NAME} ."]

The problem was lack of single quotes around build-args' values. Basically, in this context a build-arg value is a single string, not a key-value pair