Add workaround for latest maven-install plugin

(cherry picked from commit afcfd26)

tycho-core/src/main/java/org/eclipse/tycho/core/osgitools/EclipseRepositoryProject.java

@@ -16,7 +16,10 @@
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Properties;
 
+import org.apache.maven.execution.MavenSession;
+import org.apache.maven.project.MavenProject;
 import org.codehaus.plexus.component.annotations.Component;
 import org.eclipse.tycho.ArtifactKey;
 import org.eclipse.tycho.DefaultArtifactKey;
@@ -70,10 +73,22 @@ public void walk(ArtifactDependencyVisitor visitor) {
         };
     }
 
+    @Override
+    public void setupProject(MavenSession session, MavenProject project) {
+        super.setupProject(session, project);
+        //This is a hack for install plugin that requires a "main" artifact and otherwise fails
+        //but a repository project may only attaches additional artifacts, e.g updatesite / products 
+        Properties properties = project.getProperties();
+        if (properties.getProperty("allowIncompleteProjects") == null) {
+            properties.setProperty("allowIncompleteProjects", "true");
+        }
+    }
+
     /**
      * Parses the category configuration files
      *
-     * @param project the project containing the category files
+     * @param project
+     *            the project containing the category files
      * @return the parsed category configurations
      */
     public List<Category> loadCategories(final ReactorProject project) {
@@ -83,7 +98,8 @@ public List<Category> loadCategories(final ReactorProject project) {
     /**
      * Parses the category configuration files
      *
-     * @param categoriesDirectory the directory where the category files are stored
+     * @param categoriesDirectory
+     *            the directory where the category files are stored
      * @return the parsed category configurations
      */
     public List<Category> loadCategories(final File categoriesDirectory) {
@@ -130,10 +146,11 @@ private List<File> getCategoryFiles(final File basedir) {
     }
 
     /**
-     * Looks for all files at the base of the project that extension is ".product"
-     * Duplicated in the P2GeneratorImpl
+     * Looks for all files at the base of the project that extension is ".product" Duplicated in the
+     * P2GeneratorImpl
      *
-     * @param project the project containing the product files
+     * @param project
+     *            the project containing the product files
      * @return The list of product files to parse for an eclipse-repository project
      */
     public List<File> getProductFiles(final ReactorProject project) {
@@ -144,7 +161,8 @@ public List<File> getProductFiles(final ReactorProject project) {
     /**
      * Looks for all files with the extension ".product" under a specific directory.
      *
-     * @param basedir the directory containing the product files
+     * @param basedir
+     *            the directory containing the product files
      * @return The list of product files to parse for an eclipse-repository project
      */
     public List<File> getProductFiles(final File basedir) {