Do not inject sources into the maven model

Currently we inject sources that are resolved from the targetplatform,
but this can lead to additional downloads and confuses other tools.

This now skip injecting source to the maven model as this is usually not
done when working with maven.

Author: laeubi

tycho-core/src/main/java/org/eclipse/tycho/core/maven/MavenDependencyInjector.java

@@ -117,6 +117,10 @@ public static void injectMavenDependencies(MavenProject project, DependencyArtif
         MavenDependencyInjector generator = new MavenDependencyInjector(project, bundleReader, descriptorMapping,
                 logger);
         for (ArtifactDescriptor artifact : dependencies.getArtifacts()) {
+            if (TychoConstants.CLASSIFIER_SOURCES.equals(artifact.getClassifier())) {
+                //there is no need to struggle with source when we inject dependencies
+                continue;
+            }
             generator.addDependency(artifact, Artifact.SCOPE_COMPILE);
         }
         if (testDependencies != null) {