fix: Update System.env syntax for Gradle 9 compatibility

[dbwiddis]

This PR updates the Gradle build files to fix compatibility with Gradle 9.

Problem

The current syntax using $System.env.VARIABLE_NAME for accessing environment variables is not compatible with Gradle 9.

This format is used in this repository for Sonatype credentials for SNAPSHOT publication. This fails with under Gradle 9.

credentials {
    username = "$System.env.SONATYPE_USERNAME"
    password = "$System.env.SONATYPE_PASSWORD"
}

See example failed workflow here.

Solution

Update to use the System.getenv() method instead:

credentials {
    username = System.getenv("SONATYPE_USERNAME")
    password = System.getenv("SONATYPE_PASSWORD")
}

Example fix which restored successful snapshots: opensearch-project/opensearch-remote-metadata-sdk#245

[jzonthemtn]

I can't imagine this change is what is causing the yaml rest tests to fail on a couple of those builds.

[epugh]

@dbwiddis can you sign your commit and then I'll merge!

[dbwiddis]

@dbwiddis can you sign your commit and then I'll merge!

It looks signed off to me? DCO passes?
7f64d22

[epugh]

@dbwiddis can you sign your commit and then I'll merge!

It looks signed off to me? DCO passes? 7f64d22

DCO yes, but verified missing:

[dbwiddis]

Done!