cmd/cue: -e does not know about standard builtins

[myitcv]

What version of CUE are you using (cue version)?

$ cue version
cue version +37bf801b linux/amd64

Does this issue reproduce with the latest release?

Yes

What did you do?

exec cue export --out text -e 'yaml.MarshalStream(X)' x.cue

-- x.cue --
X: [
	{
		a: 1
	},
	{
		b: 2
	},
]

gives:

reference "yaml" not found:
    --expression:1:1

This is a regression from v0.2.2

What did you expect to see?

Per v0.2.2:

a: 1
---
b: 2

What did you see instead?

As above; an error.

[cueckoo]

This issue has been migrated to cue-lang/cue#999.

For more details about CUE's migration to a new home, please see cue-lang/cue#1078.