[direnv] add quotations around devbox-shellenv-init-hook call

[savil]

Summary

@Lagoja is reporting an error of the form:

./.envrc:8: go: command not found

In our generated code we have eval $(devbox shellenv --init-hook).

The error is occuring because bash is executing the devbox shellenv --init-hook prior
to doing the eval. Any $(<bash command>) within the output of devbox shellenv
will also be eagerly evaluated (via bash command substituion) prior to the
final eval.

With the change: we add quotations around the $(devbox shellenv --init-hook) so
that the eval operation will execute the devbox shellenv --init-hook. And eval
each line in the output as it goes.

This way, a line in our init-hook like export GOROOT="(go env GOROOT)" will have access to the go
binary prior to go env GOROOT being executed (a prior line from devbox shellenv adds the
go binary to PATH).

How was it tested?

1. removed go from my zshrc PATH.
2. did rm .envrc and direnv revoke . to reset.
3. devbox generate direnv and direnv allow .
4. cd .. to exit directory and cd devbox to enter directory

BEFORE: saw error above
AFTER: no error seen

[savil]

Current dependencies on/for this PR:

• main
  • PR [direnv] add quotations around devbox-shellenv-init-hook call #913 👈

This comment was auto-generated by Graphite.

[Lagoja]

LGTM, I know there were a few versions of that line floating around, so @gcurtis and @LucilleH to verify this is the one we want?