can't use docker compose file with a $PWD in a mount path

[a4z]

Description

A docker compose file with the following volumes part:

 volumes:
    - $PWD:/var/project

does not work with nerdctl compose

> nerdctl compose up     
WARN[0000] The "PWD" variable is not set. Defaulting to a blank string. 
FATA[0000] 1 error(s) decoding:

* error decoding 'Volumes[2]': invalid spec: :/var/project: empty section between colons 

Steps to reproduce the issue

use a volume like in the example above in a docker compose file and run nerdctl compose up

this does unfortunately not work

Describe the results you received and expected

running the compose file with the mount as docker does it

What version of nerdctl are you using?

 nerdctl version
Client:
 Version:	v0.19.0
 OS/Arch:	linux/arm64
 Git commit:	c94a967a2c481c24c1305d0a816d71fccbd97344

Server:
 containerd:
  Version:	v1.5.11
  GitCommit:	3df54a852345ae127d1fa3092b95168e4a88e2f8

Are you using a variant of nerdctl? (e.g., Rancher Desktop)

Rancher Desktop for macOS

Host information

 nerdctl info
Client:
 Namespace:	default
 Debug Mode:	false

Server:
 Server Version: v1.5.11
 Storage Driver: overlayfs
 Logging Driver: json-file
 Cgroup Driver: cgroupfs
 Cgroup Version: 1
 Plugins:
  Log: json-file
  Storage: native overlayfs
 Security Options:
  seccomp
   Profile: default
 Kernel Version: 5.15.32-0-virt
 Operating System: Alpine Linux v3.15
 OSType: linux
 Architecture: aarch64
 CPUs: 4
 Total Memory: 7.753GiB
 Name: lima-rancher-desktop
 ID: 4613d864-017c-43a5-985e-d27a13fcf5c0

WARNING: IPv4 forwarding is disabled
WARNING: bridge-nf-call-iptables is disabled
WARNING: bridge-nf-call-ip6tables is disabled