[BUG]: `docker build --check` complains about legacy ENV format

[amarburg]

Issue Description

Running docker build --check produces this warning:

WARNING: LegacyKeyValueFormat - https://docs.docker.com/go/dockerfile/rule/legacy-key-value-format/
"ENV key=value" should be used instead of legacy "ENV key value" format
Dockerfile:214
--------------------
 212 |     
 213 |     # Env vars for the nvidia-container-runtime.
 214 | >>> ENV NVIDIA_VISIBLE_DEVICES all
 215 |     ENV NVIDIA_DRIVER_CAPABILITIES graphics,utility,compute
 216 |     ENV QT_X11_NO_MITSHM 1
--------------------

WARNING: LegacyKeyValueFormat - https://docs.docker.com/go/dockerfile/rule/legacy-key-value-format/
"ENV key=value" should be used instead of legacy "ENV key value" format
Dockerfile:215
--------------------
 213 |     # Env vars for the nvidia-container-runtime.
 214 |     ENV NVIDIA_VISIBLE_DEVICES all
 215 | >>> ENV NVIDIA_DRIVER_CAPABILITIES graphics,utility,compute
 216 |     ENV QT_X11_NO_MITSHM 1
 217 |     
--------------------

WARNING: LegacyKeyValueFormat - https://docs.docker.com/go/dockerfile/rule/legacy-key-value-format/
"ENV key=value" should be used instead of legacy "ENV key value" format
Dockerfile:216
--------------------
 214 |     ENV NVIDIA_VISIBLE_DEVICES all
 215 |     ENV NVIDIA_DRIVER_CAPABILITIES graphics,utility,compute
 216 | >>> ENV QT_X11_NO_MITSHM 1
 217 |     
--------------------

Steps to Reproduce

cd .docker && docker build --check .

Expected Behavior

No warnings

Error Message

see above

Runtime Environment

Ubuntu 20.04 on amd64 running Docker version 27.1.1, build 6312585

Additional Context

No response