RATIS-2454. Findbugs summary is empty despite violations

[adoroszlai]

What changes were proposed in this pull request?

Even if there are findbugs failures, summary.txt is not created:

No files were found with the provided path: target/findbugs

because Spotbugs CLI commands (required for post-processing output created by Maven run) are not available in GitHub.

Install Spotbugs in subdirectory of .dev-tools (installation script taken from Ozone, where it has been in use for few years).

https://issues.apache.org/jira/browse/RATIS-2454

How was this patch tested?

Current state (without violations):

$ ./dev-support/checks/findbugs.sh
mkdir: created directory '.dev-tools'
mkdir: created directory '.dev-tools/spotbugs'
...
Installed spotbugs in .dev-tools/spotbugs
...
[INFO] BUILD SUCCESS
...

$ echo $?
0

$ ls -1s target/findbugs
total 448
  4 failures
 68 output.log
236 summary.html
  0 summary.txt
140 summary.xml

$ cat target/findbugs/failures
0

With some violations introduced temporarily:

$ git revert --no-commit eb465d56
$ git reset HEAD -- ratis-server/dev-support/findbugsExcludeFile.xml
$ git checkout -- ratis-server/dev-support/findbugsExcludeFile.xml

$ ./dev-support/checks/findbugs.sh
...
[INFO] BUILD SUCCESS
...

$ echo $?
1

$ ls -1s target/findbugs                                          
total 464
  4 failures
 68 output.log
240 summary.html
  4 summary.txt
148 summary.xml

$ cat target/findbugs/failures
0

$ cat target/findbugs/summary.txt 
M B CT: Exception thrown in class org.apache.ratis.server.impl.LeaderElection at new org.apache.ratis.server.impl.LeaderElection(LeaderElection$ServerInterface, boolean) will leave the constructor. The object under construction remains partially initialized and may be vulnerable to Finalizer attacks.  At LeaderElection.java:[line 324]
M B CT: Exception thrown in class org.apache.ratis.server.impl.LeaderElection at new org.apache.ratis.server.impl.LeaderElection(RaftServerImpl, boolean) will leave the constructor. The object under construction remains partially initialized and may be vulnerable to Finalizer attacks.  At LeaderElection.java:[line 310]
M B CT: Exception thrown in class org.apache.ratis.server.raftlog.segmented.SegmentedRaftLogReader at new org.apache.ratis.server.raftlog.segmented.SegmentedRaftLogReader(File, SizeInBytes, SegmentedRaftLogMetrics) will leave the constructor. The object under construction remains partially initialized and may be vulnerable to Finalizer attacks.  At SegmentedRaftLogReader.java:[line 155]
M B CT: Exception thrown in class org.apache.ratis.server.storage.FileChunkReader at new org.apache.ratis.server.storage.FileChunkReader(FileInfo, Path) will leave the constructor. The object under construction remains partially initialized and may be vulnerable to Finalizer attacks.  At FileChunkReader.java:[line 60]

CI:
https://github.com/adoroszlai/ratis/actions/runs/23641934315

[spacemonkd]

Thanks for the patch @adoroszlai, LGTM +1
@szetszwo could you take a look at this as well please?