[Elastic Agent] Keep debug symbols, no inline and no optimisations for dev builds

[AndersonQ]

What does this PR do?

When the agent is built for development it keeps the debug symbols, do not inline nor optimize so it's possible to debug using delve.

It also fixes a typo.

Why is it important?

Improves developer experience by making it ready for debug when building for development.

Checklist

• [ x] My code follows the style guidelines of this project
• [ x] I have commented my code, particularly in hard-to-understand areas
• [ x] I have made corresponding changes to the documentation
• [ x] I have made corresponding change to the default configuration files
• [ ] I have added tests that prove my fix is effective or that my feature works
• [ ] I have added an entry in CHANGELOG.next.asciidoc or CHANGELOG-developer.next.asciidoc.

How to test this PR locally

Build with DEV=true, then run it with delve and connect to remote debug

Using GoLand, you can run the elastic-agent as below and use the Go Remote to Run/Debug the agent.

dlv --listen=:2345 --headless=true --api-version=2 --accept-multiclient exec ./elastic-agent

Related issues

[elasticmachine]

Pinging @elastic/elastic-agent-control-plane (Team:Elastic-Agent-Control-Plane)

[jlind23]

@AndersonQ is this one good to be reviewed?

[AndersonQ]

/test metricbeat-windows-2016-windows-2016

[AndersonQ]

@jlind23 yes, it's ready for review. The failing tests seem to be unrelated to my changes. But I'm looking at them now

[elasticmachine]

💚 Build Succeeded

the below badges are clickable and redirect to their specific view in the CI or DOCS

Expand to view the summary

Build stats

• Start Time: 2022-01-25T15:55:32.916+0000

• Duration: 31 min 27 sec

• Commit: 7a03a0c

Test stats 🧪

Test	Results
Failed	0
Passed	706
Skipped	241
Total	947

💚 Flaky test report

Tests succeeded.

🤖 GitHub comments

To re-run your PR in the CI, just comment with:

• /test : Re-trigger the build.

• /package : Generate the packages and run the E2E tests.

• /beats-tester : Run the installation tests with beats-tester.

• run elasticsearch-ci/docs : Re-trigger the docs validation. (use unformatted text in the comment!)

[ph]

Changes LGTM, I've looked at the test suite and this looks like an issue with the python environment on windows. Two possible reasons:

1. The Windows images changed ? @v1v
2. We are missing the venv python module in our requirements https://docs.python.org/3/library/venv.html

Maybe both are true?

[v1v]

The runtime configuration script to prepare the context failed but it didn't exit 1, therefore it ran the mage build/test

[2022-01-25T11:08:13.948Z] Failures
[2022-01-25T11:08:13.948Z]  - python (exited 1) - python not installed. An error occurred during installation:
[2022-01-25T11:08:13.948Z]  The operation has timed out

https://beats-ci.elastic.co/blue/organizations/jenkins/Beats%2Fbeats%2FPR-29961/detail/PR-29961/2/pipeline/#step-3696-log-39

The behaviour then fallbacks to the current installed software in the Worker, and it seems python2 is the default one.

For the moment, just type /test again, and I'll raise an issue to track the error and then figure out why it didn't return error 1 but kept running

[ph]

/test