Support MAVEN_CLI_OPTS in gemnasium-maven

What does this MR do?

Adds MAVEN_CLI_OPTS to gemnasium-maven analyzer.

Implementation plan

Update the dependency scanner and its maven plugin to accept a new environment variable. This will allow users to parametrize their pom.xml.

For example, when a user needs to scan packages in a private repo, they will be able to supply a settings.xml file that supplies user credentials as variables which can then be injected as environment variables when the pipeline executes.

pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
  <modelVersion>4.0.0</modelVersion>
  ...
  <repositories>
    <repository>
        <id>privaterepo</id>
        <url>https://private.repo.com/</url>
    </repository>
  </repositories>
  ...
</project>

settings.xml

...
<servers>
	<server>
		<id>privaterepo</id>
		<username>${privaterepo.username}</username>
		<password>${privaterepo.bar}</password>
	</server>
</servers>
...

Supplying the run dependent variables thusly:

MAVEN_CLI_OPTS="--settings settings.xml -Dprivaterepo.usernam=foo -Dprivaterepo.password=bar"

Testing

• Test by running against the local project with MAVEN_CLI_OPTS supplied (e.g. GOOS=linux go build -o analyzer && docker build -t analyzer . && docker run --rm --volume "$PWD"/test/fixtures:/tmp/project --env CI_PROJECT_DIR=/tmp/project --env MAVEN_CLI_OPTS="-X" analyzer /analyzer run) you should see verbose output when supplied the -X option to maven.

Related issues

#11166 (closed) - Add support for MAVEN_CLI_OPTS