Bug 53582 Rebuild Project are not run in the background?
The "Build All" and "Rebuild All" actions are run in the background, but the "Build Project" and "Rebuild Project" actions aren't. This is not consistent and I was surprised to get a modal dialog when performing a "Rebuild Project".
bundles/org.eclipse.ui.ide/extensions/org/eclipse/ui/actions/BuildAction.java
IProject project = resource.getProject();
			if (project != null) {
				if (!projectsToBuild.contains(project)) {
					if (hasBuilder(project)) {
						projectsToBuild.add(project);
					}
				}
			}
		}
	}
	return projectsToBuild;
}
/**
 * Returns whether there are builders configured on the given project.
 *
 * @return <code>true</code> if it has builders,
 *   <code>false</code> if not, or if this couldn't be determined
 */
boolean hasBuilder(IProject project) {
	try {
		ICommand[] commands = project.getDescription().getBuildSpec();
		if (commands.length > 0) {
			return true;
		}
	}
	catch (CoreException e) {