Change way to generate initfs for kernel
Created by: kolipka
this change should be merged along with corresponding PR in kernel (https://github.com/redox-os/kernel/pull/3)
Problem: [describe the problem you try to solve with this PR.] Decouple kernel from whole redox. It can be compiled on its own. Changing initfs folder location does not require modifications in kernel
Solution: [describe carefully what you change by this PR.] build scripts are changed to send initfs folder as a parameter ( env var: INITFS_FOLDER) to kernel build.rs script
Changes introduced by this pull request: As described above
Drawbacks: [if any, describe the drawbacks of this pull request.] has to be merged along with change in kernel repo
TODOs: [what is not done yet.] N/A
Fixes: [what issues this fixes.] N/A
State: [the state of this PR, e.g. WIP, ready, etc.] N/A
Blocking/related: [issues or PRs blocking or being related to this issue.] N/A
Other: [optional: for other relevant information that should be known or cannot be described in the other fields.] N/A
The above template is not necessary for smaller PRs.