[BEAM-12763] Remove redundant build from copy path in copyJavaThirdPartyLicenses rule

[lostluck]

Without this change a redundant /build/ appears on the copy path, leading to the rule doing nothing.

Before, after clearing sdks/java/container/build and sdks/java/container/java8/build.

> Task :sdks:java:container:java8:copyJavaThirdPartyLicenses NO-SOURCE
file or directory '/home/rebo/git/src/github.com/apache/beam/sdks/java/container/build/build/target/third_party_licenses', not found
Skipping task ':sdks:java:container:java8:copyJavaThirdPartyLicenses' as it has no source files and no previous output files.
:sdks:java:container:java8:copyJavaThirdPartyLicenses (Thread[Execution worker for ':',5,main]) completed. Took 0.0 secs.
:sdks:java:container:java8:dockerPrepare (Thread[Execution worker for ':',5,main]) started.

The job then fails to build the Dockerfile.

Step 13/18 : ADD target/third_party_licenses /opt/apache/beam/third_party_licenses/
ADD failed: stat /var/lib/docker/tmp/docker-builder213254890/target/third_party_licenses: no such file or directory

However, a subsequent run succeeds but still produces the same error:

> Task :sdks:java:container:java8:copyJavaThirdPartyLicenses NO-SOURCE
file or directory '/home/rebo/git/src/github.com/apache/beam/sdks/java/container/build/build/target/third_party_licenses', not found
Skipping task ':sdks:java:container:java8:copyJavaThirdPartyLicenses' as it has no source files and no previous output files.
:sdks:java:container:java8:copyJavaThirdPartyLicenses (Thread[Execution worker for ':' Thread 3,5,main]) completed. Took 0.0 secs.
:sdks:java:container:java8:copyLicenses (Thread[Execution worker for ':' Thread 3,5,main]) started.

It's not clear why the 2nd run succeeds at all, or how the license files are making it the second time around, however, this PR resolves the issue immeadiately.

After the fix in this PR, the rule produces the following

> Task :sdks:java:container:java8:copyJavaThirdPartyLicenses
Caching disabled for task ':sdks:java:container:java8:copyJavaThirdPartyLicenses' because:
  Caching has not been enabled for the task
Task ':sdks:java:container:java8:copyJavaThirdPartyLicenses' is not up-to-date because:
  No history is available.
Watching 12568 directories to track changes
Watching 12859 directories to track changes
:sdks:java:container:java8:copyJavaThirdPartyLicenses (Thread[Execution worker for ':' Thread 3,5,main]) completed. Took 0.341 secs.
:sdks:java:container:java8:copyDockerfileDependencies (Thread[Execution worker for ':' Thread 3,5,main]) started.

and the Dockerfile succeeds on the first try.

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ValidatesRunner compliance status (on master branch)

Lang	ULR	Dataflow	Flink	Samza	Spark	Twister2
Go	---					---
Java
Python	---					---
XLang						---

Examples testing status on various runners

Lang	ULR	Dataflow	Flink	Samza	Spark	Twister2
Go	---	---	---	---	---	---	---
Java	---		---	---	---	---	---
Python	---	---	---	---	---	---	---
XLang	---	---	---	---	---	---	---

Post-Commit SDK/Transform Integration Tests Status (on master branch)

Go	Java	Python

Pre-Commit Tests Status (on master branch)

---	Java	Python	Go	Website	Whitespace	Typescript
Non-portable
Portable	---			---	---	---

See .test-infra/jenkins/README for trigger phrase, status and link of all Jenkins jobs.

GitHub Actions Tests Status (on master branch)

See CI.md for more information about GitHub Actions CI.

[youngoli]

This PR is fixing an issue that occurs when building a container with a clean docker cache. So if you follow these steps you can probably replicate it:

1. Delete sdks/java/container/build and sdks/java/container/java8/build. (You might have to avoid some read-only directories, just delete everything else)
2. Run ./gradlew -Pdocker-pull-licenses :sdks:java:container:java8:docker. It should fail with a complaint about a missing third_party_license directory.
3. Run the same command again. It should work this time.

The specific error that it fails with is:

Step 13/18 : ADD target/third_party_licenses /opt/apache/beam/third_party_licenses/
[...]
ADD failed: stat /var/lib/docker/tmp/docker-builder099525146/target/third_party_licenses: no such file or directory

I can confirm that making this change fixes the issue on my machine at least.

[lostluck]

Run Go Flink ValidatesRunner

[lostluck]

Run Java_Examples_Dataflow PreCommit

[lostluck]

R: @youngoli
cc: @emilymye