Add JENKINS_HOME_PATH as default JENKINS_HOME always returns /var/jenkins_home and update jdk14

[peterzhuamazon]

Signed-off-by: Peter Zhu zhujiaxi@amazon.com

Description

Add JENKINS_HOME_PATH as default JENKINS_HOME always returns /var/jenkins_home.
This is a backend settings required to support windows gradle check.
Due to LINUX and Windows having different home directory for Jenkins, we need a variable to export the value.
The issue is, the default JENKINS_HOME variable is always returning /var/jenkins_home regardless of the platform.

By adding a node var for the agents it will dynamically display the root based on the platform remote fs.

Thanks.

Issues Resolved

opensearch-project/opensearch-build#2306

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.
For more information on following Developer Certificate of Origin and signing off your commits, please check here.

[peterzhuamazon]

New follow up enhancement issue here:

• [Enhancement] Adding an entrypoint to allow custom Global Tools modifications #216

[peterzhuamazon]

Adding more context:

• We need to add jdk14 is because we need it for LINUX/Windows gradle check, task bwcTest with 1.x version clusters. Once we do not support 1.x anymore, we can safely remove this temporary solution.
• As for why jdk14 cannot be automatically installed on jenkins, see here: [BUG] Gradle Check failed due to jdk14 no long available opensearch-build#2604.
• We move the artifacts on ci.opensearch.org is to make sure it is consistent between linux and windows version of the jdk, and strip the leading subfolder so jenkins can natually unzip it in the same directory.
• Since jdk14 is deprecated now we also need to preserve the binaries for the time being.

Thanks.