Magepack - Fix bundle and generate files permission

[ihor-sviziev]

This is follow-up on #6.
Looks like it didn't help because we're getting an error:

~ warden env exec magepack bundle
OCI runtime exec failed: exec failed: unable to start container process: exec: "bundle": executable file not found in $PATH: unknown


~ warden env exec magepack generate
OCI runtime exec failed: exec failed: unable to start container process: exec: "generate": executable file not found in $PATH: unknown

I checked, looks like these files don't have proper permissions, so this PR fixes it.

Fixes wardenenv/warden#596

[ihor-sviziev]

@navarr could you pls review?

[ihor-sviziev]

Just checked - now it works as expected after warden env pull && warden env up