Environment variables not properly propagated in the sandbox environment

Summary

When setting environment variable LD_LIBRARY_PATH to an element, this variable is not used.

Steps to reproduce

This element fails:

kind: manual

depends:
  - filename: base.bst
    junction: freedesktop-sdk.bst
    type: build

environment:
  LD_LIBRARY_PATH: /foo/bar

config:
  build-commands:
    - |
      [ "${LD_LIBRARY_PATH}" = /foo/bar ]

What is the current bug behavior?

The build of the element fails.

What is the expected correct behavior?

The build of the element does not fail.

Relevant logs and/or screenshots

Possible fixes

The current way environment variables are used is to call Bubblewrap with it instead of telling it to use that environment for the command run by Bubblewrap.

There might be other, consequence for this approach. For instance if the local installation of Bubblewrap requires some environment variable to be set to run correctly, this will not be the case. Bubblewrap will be run with the environment for the element.

Here is what need to be fixed:

• Use --settenv and --unsetenv in Bubblewrap command line to set environment.
• Use user environment to call Bubblewrap.

Other relevant information

• BuildStream version affected: /milestone %BuildStream_v1.2

---