Make dev-env.sh script work on Linux

[mdonkers]

What this PR does / why we need it:
Currently the dev-env.sh script, used for deploying to a local Minikube, only works on MacOS unless both kubectl and kustomize are installed.

Which issue this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close that issue when PR gets merged): fixes #
This PR works somewhat to a more supported setup by just using kubectl when that is available, since the latest (> v1.14) has kustomize by default included. So no separate kustomize tool needs to be installed via Homebrew. So this lowers also the requirements for Linux, as only kubectl needs to be present on the system already.

Special notes for your reviewer:
The kubectl kustomize command does not have the option to set fields in an existing kustomize.yaml file. Tried to use overlays within the ${ROOT} directory but that leads to 'cycle detected' errors. So instead opted to use sed to replace variables within the kustomize.yaml file directly as the kustomize command itself would do.

[k8s-ci-robot]

Welcome @mdonkers!

It looks like this is your first PR to kubernetes/ingress-nginx 🎉. Please refer to our pull request process documentation to help your PR have a smooth ride to approval.

You will be prompted by a bot to use commands during the review process. Do not be afraid to follow the prompts! It is okay to experiment. Here is the bot commands documentation.

You can also check if kubernetes/ingress-nginx has its own contribution guidelines.

You may want to refer to our testing guide if you run into trouble with your tests not passing.

If you are having difficulty getting your pull request seen, please follow the recommended escalation practices. Also, for tips and tricks in the contribution process you may want to read the Kubernetes contributor cheat sheet. We want to make sure your contribution gets all the attention it needs!

Thank you, and welcome to Kubernetes. 😃

[k8s-ci-robot]

Hi @mdonkers. Thanks for your PR.

I'm waiting for a kubernetes member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

I understand the commands that are listed here.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[aledbf]

/ok-to-test

[codecov-io]

Codecov Report

❗ No coverage uploaded for pull request base (master@771fc9f). Click here to learn what that means.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master    #4290   +/-   ##
=========================================
  Coverage          ?   58.31%           
=========================================
  Files             ?       87           
  Lines             ?     6472           
  Branches          ?        0           
=========================================
  Hits              ?     3774           
  Misses            ?     2272           
  Partials          ?      426

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 771fc9f...a4d92f4. Read the comment docs.

[aledbf]

Make dev-env.sh script work on Linux

Please change the title. The script dev-env.sh works on Linux. Something like Use included kustomize command in kubectl if available. Besides that this LGTM

[aledbf]

/lgtm

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: aledbf, mdonkers

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [aledbf]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment