ProjectReferences: ts-loader doesnt build dependent projects

Expected Behaviour

Based on this highly anticipated and recently merged PR: https://github.com/TypeStrong/ts-loader/pull/935 by @sheetalkamat I would expect ts-loader to build dependent projects if projectReferences: true.

Actual Behaviour

Dependent project reference is not built when building project.

The test projectReferencesNotBuilt referenced in the "steps to reproduce" section seems to account for the fact that the dependent project may not already be built. However, the expected output of that test is just the TypeScript error saying the project hasn't been built and to run tsc --build to build the dependent project. I would expect the projectReferences config option to basically run the API equivalent of tsc --build.

Actual application error:

Module build failed (from ../node_modules/ts-loader/index.js):
Error: Could not find output JavaScript file for input assets/scripts/api/api.ts (looked at assets/scripts/lib/api/api.js).
The input file is part of a project reference located at tsconfig.json, so ts-loader is looking for the project’s pre-built output on disk. Try running `tsc --build` to build project references.
    at successLoader (/src/node_modules/ts-loader/dist/index.js:46:19)
    at Object.loader (/src/node_modules/ts-loader/dist/index.js:22:12)
 @ ./portal/assets/scripts/actions/Dashboard.tsx 28:0-129 42:15-37 43:19-37 44:23-45 45:16-41
 @ ./portal/assets/scripts/router.ts
 @ ./portal/assets/scripts/index.tsx
./assets/scripts/api/methods.ts

Steps to Reproduce the Problem

Typescript: v3.6.3
ts-loader: v6.1.0

yarn run comparison-tests --single-test projectReferencesNotBuilt                                                    09/17 15:40:15 121.372s
yarn run v1.17.3
$ tsc --project "./test/comparison-tests" && npm link ./test/comparison-tests/testLib && node test/comparison-tests/run-tests.js --single-test projectReferencesNotBuilt
npm WARN lib@0.0.1 No repository field.
npm WARN lib@0.0.1 No license field.

up to date in 0.276s
found 0 vulnerabilities

/Users/justin/.fnm/node-versions/v12.3.1/installation/lib/node_modules/lib -> /src/ts-loader/test/comparison-tests/testLib
/src/ts-loader/node_modules/lib -> /Users/justin/.fnm/node-versions/v12.3.1/installation/lib/node_modules/lib -> /src/ts-loader/test/comparison-tests/testLib

-------------------------------------------------------------------------

Starting to run test suites...



  projectReferencesNotBuilt
    1) should have the correct output
    ✓ should work with transpileOnly (292ms)


  1 passing (2s)
  1 failing

  1) projectReferencesNotBuilt
       should have the correct output:

      Uncaught AssertionError [ERR_ASSERTION]: bundle.js is different between actual and expected
      + expected - actual

       /*!**********!*/
         !*** ./lib/index.ts ***!
         /**********/
       /*! no static exports found */
      -/***/ (function(module, exports, __webpack_require__) {
      -"use strict";
      -eval("
      -exports.__esModule = true;
      -exports.lib = {
      -    one: 1,
      -    two: 2,
      -    three: 3
      -};
      +/***/ (function(module, exports) {
      +eval("throw new Error(/"Module build failed (fromts-loader):/nError: Could not find output JavaScript file for input lib/index.ts (looked at lib/index.js)./nThe input file is part of a project reference located at lib/tsconfig.json, so ts-loader is looking for the project’s pre-built output on disk. Try running `tsc --build` to build project references./n    at successLoader (ts-loader)/n    at Object.loader (ts-loader)/");
       /# sourceURL=webpack://./lib/index.ts?");
       /***/ })
       /******/ });

      at compareActualAndExpected (test/comparison-tests/create-and-execute-test.js:467:16)
      at /src/ts-loader/test/comparison-tests/create-and-execute-test.js:333:13
      at Array.forEach (<anonymous>)
      at compareFiles (test/comparison-tests/create-and-execute-test.js:329:31)
      at Watching.handler (test/comparison-tests/create-and-execute-test.js:194:9)
      at /src/ts-loader/node_modules/webpack/lib/Watching.js:100:9
      at AsyncSeriesHook.eval [as callAsync] (eval at create (node_modules/webpack/node_modules/tapable/lib/HookCodeFactory.js:32:10), <anonymous>:6:1)
      at AsyncSeriesHook.lazyCompileHook (node_modules/webpack/node_modules/tapable/lib/Hook.js:154:20)
      at Watching._done (node_modules/webpack/lib/Watching.js:99:28)
      at /src/ts-loader/node_modules/webpack/lib/Watching.js:73:19
      at Compiler.emitRecords (node_modules/webpack/lib/Compiler.js:366:39)
      at /src/ts-loader/node_modules/webpack/lib/Watching.js:54:20
      at /src/ts-loader/node_modules/webpack/lib/Compiler.js:352:14
      at AsyncSeriesHook.eval [as callAsync] (eval at create (node_modules/webpack/node_modules/tapable/lib/HookCodeFactory.js:32:10), <anonymous>:6:1)
      at AsyncSeriesHook.lazyCompileHook (node_modules/webpack/node_modules/tapable/lib/Hook.js:154:20)
      at /src/ts-loader/node_modules/webpack/lib/Compiler.js:349:27
      at done (node_modules/neo-async/async.js:2854:11)
      at /src/ts-loader/node_modules/neo-async/async.js:2805:7
      at /src/ts-loader/node_modules/graceful-fs/graceful-fs.js:45:10
      at FSReqCallback.oncomplete (fs.js:137:23)

Start with the projectReferencesNotBuilt comparison test in test/comparison-tests and the loader entry points shown in index.js and dist/index.js. Reproduce it with yarn run comparison-tests --single-test projectReferencesNotBuilt, then use the expected bundle output to verify that dependent project references build instead of producing the pre-built-output error.