6c4fbb7738
By default, exec uses the environment of the current process, however,
if `exec.Env` is not `nil`, the environment is discarded:
e73f489494/src/os/exec/exec.go (L57-L60)
> If Env is nil, the new process uses the current process's environment.
When adding a new environment variable, prepend the current environment,
to make sure it is not discarded.
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>