addInRepoAddon(inRepoAddonPkg) {
    if (!this.inRepoAddons) {
      this.inRepoAddons = [];
    }
    this.inRepoAddons.push(inRepoAddonPkg);
  }
Add a reference to an in-repo addon PackageInfo object.

@protected
@method addInRepoAddon
@param {PackageInfo} inRepoAddonPkg the PackageInfo for the in-repo addon
@return null