Skip relativePaths containing colon as that fails on Windows

[timtebeek]

Fixes #3167

artemis-pom-2.28.0.pom contains a weird relative path: https://repo1.maven.org/maven2/org/apache/activemq/artemis-pom/2.28.0/artemis-pom-2.28.0.pom

<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>
    <groupId>org.apache.activemq</groupId>
    <artifactId>artemis-pom</artifactId>
    <packaging>pom</packaging>
    <version>2.28.0</version>
    <parent>
        <groupId>org.apache</groupId>
        <artifactId>apache</artifactId>
        <version>27</version>
        <relativePath>org.apache:apache</relativePath>
    </parent>

This worked okay-ish on Linux/Mac, as passing the relativePath into Paths.get(relativePath, "pom.xml") will just result in a null maybeLocalPom. On Windows however, a colon is not valid to pass into Paths.get(..), and it fails with the reported exception.

Since we were effectively ignoring the relative path on Mac/Linux before, we might as well skip it entirely for Windows as well.

[timtebeek]

Writing a test that fails was surprisingly hard, especially as I don't have access to a Windows machine. Hence a code only change, as we also don't run on Windows in CI either.

[knutwannheden]

LGTM 👍