Cache gradle in GitHub workflows

[trivikr]

Background

• These change add configuration to cache and restore gradle cache in GitHub workflows
• They're important as they shorten the time required for running CI. They also ensure CI can go through if gradle is down.

Testing

CI is successful

Before

Gradle build took 9m 27s
https://github.com/smithy-lang/smithy/actions/runs/17485026040/job/49702493915?pr=2767

Gradle is downloaded from network

Downloading https://services.gradle.org/distributions/gradle-8.14.3-bin.zip
.............10%.............20%.............30%.............40%.............50%.............60%.............70%.............80%.............90%..............100%

After

Gradle build took 9m 7s
https://github.com/smithy-lang/smithy/actions/runs/17657629935/job/50184162984?pr=2776

Gradle is used from cache

Cache hit for: setup-java-Linux-x64-gradle-9747105db696c51e598605430ba5768c03b834c6528543f1b60381c28225c14d
Received 20971520 of 568227640 (3.7%), 20.0 MBs/sec
Received 150994944 of 568227640 (26.6%), 72.0 MBs/sec
Received 281018368 of 568227640 (49.5%), 89.3 MBs/sec
Received 402653184 of 568227640 (70.9%), 96.0 MBs/sec
Received 536870912 of 568227640 (94.5%), 101.6 MBs/sec
Received 568227640 of 568227640 (100.0%), 100.9 MBs/sec
Cache Size: ~542 MB (568227640 B)
/usr/bin/tar -xf /home/runner/work/_temp/b8e59747-aef9-4168-9ec6-1abd4f1cf46b/cache.tzst -P -C /home/runner/work/smithy/smithy --use-compress-program unzstd
Cache restored successfully
Cache restored from key: setup-java-Linux-x64-gradle-9747105db696c51e598605430ba5768c03b834c6528543f1b60381c28225c14d

Links

• https://github.com/actions/setup-java#caching-packages-dependencies

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By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.