How can I speed up development builds while developing a linked package? (Ember/Broccoli)

Question

My Broccoli builds take up a LOT of time. ~30 seconds to build every time I change a line of js (I mean the incremental re-builds with dev server running, NOT a complete build).

Here's my situation. I have project A which is an ember addon to project B which I npm link in. As I'm developing project A, I am running ember server on project B.

EVERY SINGLE TIME that I make a change to a line of javascript in project A and rebuild, I see that the following files change in project B:

B/dist/assets/vendor.css
B/dist/assets/vendor.js
B/dist/assets/vendor.map
B/dist/assets/B.css
B/dist/assets/B.css.map

My concern is that, because I'm developing a linked package, my broccoli configuration is such that the entire node_modules is recombined into those vendor files.

Is there a way for me to configure ember/broccoli to use a separate file to compile A into and segregate it from the rest of vendor.js? B/dist/assets/A.min.css and B/dist/assets/A.min.js for example?

...or I'm a guessing at the cause of the problem incorrectly?

Thank you so much for your help in advance!

Edit: Here's some extra info as requested

Slowest Nodes (totalTime => 5% )              | Total (avg)         
----------------------------------------------+---------------------
Concat (11)                                   | 39239ms (3567 ms)   
RecastFilter (280)                            | 33127ms (118 ms)    
Babel (233)                                   | 14099ms (60 ms)     
EslintValidationFilter (5)                    | 12632ms (2526 ms)   
LessCompiler (46)                             | 7191ms (156 ms)  

Slowest Nodes (totalTime => 5% )              | Total (avg)         
----------------------------------------------+---------------------
SourceMapConcat: Concat: Vendor /asset... (1) | 36270ms             
LessCompiler (46)                             | 4029ms (87 ms)   

Here's the index.js (Of project A):

const EngineAddon = require('ember-engines/lib/engine-addon');
const TreeMerger = require('broccoli-merge-trees');
const LessCompiler = require('broccoli-less-single');
const Funnel = require('broccoli-funnel');
const path = require('path');

module.exports = EngineAddon.extend({
  name: 'ember-engine-admin-ui',
  lazyLoading: false,

  treeForVendor(tree) {
    let addonTree = this.treeGenerator(path.resolve(this.root, this.options.trees.addon));
    let compiledLessTree = new LessCompiler(addonTree, 'styles/addon.less', `styles/${this.name}.css`);
    let sidebarCSSTree = new Funnel(path.dirname(require.resolve('sidebar-v2/css/leaflet-sidebar.css')), {
      files: ['leaflet-sidebar.css'],
      destDir: 'styles'
    });

    let sidebarJSTree = new Funnel(path.dirname(require.resolve('sidebar-v2/js/leaflet-sidebar.js')), {
      files: ['leaflet-sidebar.js'],
      destDir: 'js'
    });
    return new TreeMerger([tree, compiledLessTree, sidebarCSSTree, sidebarJSTree]);
  },

  included() {
    this._super.included.apply(this, arguments);
    this.import(`vendor/styles/${this.name}.css`);
    this.import('vendor/js/leaflet-sidebar.js');
    this.import('vendor/styles/leaflet-sidebar.css');
  },

  isDevelopingAddon() {
    return true;
  }
});