Cannot build plan/wasm when function references data document and entrypoint is the package

[johanfylling]

When the following policy:

package test

foo(_) := bar
bar := 1337

is built targeting wasm or plan, with the package assigned as entrypoint:

opa build -t wasm -e "test" test.rego

we get the following error:

error: 1 error occurred: test.rego:1: rego_type_error: undefined ref: data.test.foo
	data.test.foo
	^^^^^^^^^^^^^
	have: (any) => number

[srenatus]

Build target "plan" wasn't a thing back then, but this has been reported before: #4411.