[Feature]: podman build --secret should support env as a source like buildx

[csschwe]

Feature request description

Allow use of environment variables for podman build --secret in order to maintain feature parity with buildx

Suggest potential solution

podman build --secret=id=id,env=ENVIRONMENT_VARIABLE

Have you considered any alternatives?

It is possible to write temporary files, but this does not maintain feature parity with buildx

Additional context

docker/buildx#927

https://docs.docker.com/engine/reference/commandline/buildx_build/#secret

[rhatdan]

@flouthoc PTAL
@csschwe Interested in opening a PR?

[rhatdan]

This is a buildah issue so moving it over there.

[csschwe]

Looks like this is supported on Linux currently. But does not work with podman on MacOS.

c8002d9#diff-1ff945f9566b4296b404ee43b37ff16d62f13c90fe1a1dc040693524be03ea9b

It looks like podman is not passing the environment variables as expected on MacOS

[csschwe]

#3598

[csschwe]

Based on what I am seeing I think I should re-open this as a MacOS bug with podman build --secrets when using environment variables.