[9.0](backport #7203) [CI] Fix Core DRA crossbuild

[mergify]

What does this PR do?

Fixes Core DRA snapshot build by splittion the build step into separate steps

x86_64: Elastic-Agent Core Snapshot produces:

• elastic-agent-core-9.1.0-SNAPSHOT-linux-x86_64.tar.gz
• elastic-agent-core-9.1.0-SNAPSHOT-darwin-aarch64.tar.gz
• elastic-agent-core-9.1.0-SNAPSHOT-darwin-x86_64.tar.gz
• elastic-agent-core-9.1.0-SNAPSHOT-windows-x86_64.zip

ARM: Elastic-Agent Core Snapshot produces:

• elastic-agent-core-9.1.0-SNAPSHOT-linux-arm64.tar.gz + sha + csv

Build example

Why is it important?

Checklist

• I have read and understood the pull request guidelines of this project.
• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• 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/fragments using the changelog tool
• I have added an integration test or an E2E test

Disruptive User Impact

How to test this PR locally

Related issues

Questions to ask yourself

• How are we going to support this in production?
• How are we going to measure its adoption?
• How are we going to debug this?
• What are the metrics I should take care of?
• ...

---

This is an automatic backport of pull request #7203 done by [Mergify](https://mergify.com).

[elasticmachine]

💛 Build succeeded, but was flaky

• Buildkite Build
• Commit: 82aa2c1

Failed CI Steps

• Unit tests - Windows 11

cc @pazone

[elastic-sonarqube]

Quality Gate passed

Issues
0 New issues
0 Fixed issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
No data about Duplication

See analysis details on SonarQube