Fix parallel builds [DI-128]

[kwart]

Fixes cryptic errors in other plugins when the multimodule project is built using a parallel build.

E.g.

$ mvn -T0.5C clean install -DskipTests
....
[ERROR] COMPILATION ERROR : 
[INFO] -------------------------------------------------------------
[ERROR] /home/frantisek/work/hz/repos/hazelcast-mono/hazelcast/hazelcast-spring/src/test/java/com/hazelcast/NoMixedJUnitAnnotationsInOurTestSourcesTest.java:[19,35] package com.hazelcast.test.archunit does not exist
[ERROR] /home/frantisek/work/hz/repos/hazelcast-mono/hazelcast/hazelcast-spring/src/test/java/com/hazelcast/NoMixedJUnitAnnotationsInOurTestSourcesTest.java:[20,35] package com.hazelcast.test.archunit does not exist

....
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.13.0:compile (default-compile) on project hazelcast-jet-csv: Execution default-compile of goal org.apache.maven.plugins:maven-compiler-plugin:3.13.0:compile failed: Cannot invoke "java.io.File.getPath()" because "element" is null -> [Help 1]
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.13.0:compile (default-compile) on project hazelcast-jet-s3: Execution default-compile of goal org.apache.maven.plugins:maven-compiler-plugin:3.13.0:compile failed: Cannot invoke "java.io.File.getPath()" because "element" is null -> [Help 1]
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.13.0:compile (default-compile) on project hazelcast-jet-avro: Execution default-compile of goal org.apache.maven.plugins:maven-compiler-plugin:3.13.0:compile failed: Cannot invoke "java.io.File.getPath()" because "element" is null -> [Help 1]
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.13.0:compile (default-compile) on project hazelcast-jet-cdc-debezium: Execution default-compile of goal org.apache.maven.plugins:maven-compiler-plugin:3.13.0:compile failed: Cannot invoke "java.io.File.getPath()" because "element" is null -> [Help 1]
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.13.0:testCompile (default-testCompile) on project hazelcast-spring: Compilation failure: Compilation failure: 
[ERROR] /home/frantisek/work/hz/repos/hazelcast-mono/hazelcast/hazelcast-spring/src/test/java/com/hazelcast/NoMixedJUnitAnnotationsInOurTestSourcesTest.java:[19,35] package com.hazelcast.test.archunit does not exist
[ERROR] /home/frantisek/work/hz/repos/hazelcast-mono/hazelcast/hazelcast-spring/src/test/java/com/hazelcast/NoMixedJUnitAnnotationsInOurTestSourcesTest.java:[20,35] package com.hazelcast.test.archunit does not exist

[JackPGreen]

@kwart are you able to describe what caused the issue please and how it was addressed?

[kwart]

@kwart are you able to describe what caused the issue please and how it was addressed?

During the parallel build, it sometimes happened that the artifacts within Set<Artifact> MavenProject.artifacts returned null when Artifact.getFile() was called. Some plugins don't have a null check and fail with NPEs.

My hypothesis is that the dependencies within the project (i.e. a submodule depending on another one) caused the troubles. The plugin now skips dependencies that have groupId:artifactId belonging to one of submodules. So the main part of the fix is she skip in https://github.com/hazelcast/attribution-maven-plugin/pull/75/files#diff-e69ba7d4e67ec4d2c25fdbcc0520e9b0f33ad311cb77ec3959300380fd9f89bfR45-R49

[kwart]

Sample of missing null-check in another plugin: https://github.com/apache/maven-compiler-plugin/blob/maven-compiler-plugin-3.13.0/src/main/java/org/apache/maven/plugin/compiler/CompilerMojo.java#L313