`install.environment` config is lost when recipe is published

[jrray]

Given a recipe with install.environment rules:

pkg: env/1.0.0

api: v0/package

build:
  script:
    - true

install:
  environment:
    - set: TEST
      value: test

After building this package, the recipe that is created has lost these rules:

$ spk info env/1.0.0
api: v0/package
pkg: env/1.0.0
sources:
- path: .
  exclude:
  - .git/
  - .svn/
  filter:
  - :- .gitignore
build:
  script:
  - 'true'

($ spfs read spk/spec/env/1.0.0 gives the same output.)

The rules can still be found in the src recipe ($ spk info env/1.0.0/src) but it would be better if they survived into the other recipes for visibility.