What is the problem you're trying to solve

The compose specification contains a dockerfile_inline feature that is used instead of an external dockerfile. Currently this is not supported in nerdctl.

Describe the solution you'd like

Added support for the feature.

Additional context

Given the compose.yaml:

services:
  foo:
    build:
      dockerfile_inline: |
        FROM scratch

nerdctl compose build says:

WARN[0000] Ignoring: build: [DockerfileInline]          
INFO[0000] Building image a-foo                         
FATA[0000] lstat /a/Containerfile: no such file or directory 
FATA[0000] error while building image a-foo: exit status 1 
Error: exit status 1

nerdctl version 2.0.4