fix(typescript-webpack): remove async=false option from ts-checker to avoid preload compile hang

[malept]

• I have read the contribution documentation for this project.
• I agree to follow the code of conduct that this project follows, as appropriate.
• The changes have sufficient test coverage (if applicable).
• The testsuite passes successfully on my local machine (if applicable).

Summarize your changes:

Fixes #1386.

[codecov]

Codecov Report

Merging #1497 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1497   +/-   ##
=======================================
  Coverage   75.08%   75.08%           
=======================================
  Files          73       73           
  Lines        2135     2135           
  Branches      398      398           
=======================================
  Hits         1603     1603           
  Misses        408      408           
  Partials      124      124

Impacted Files	Coverage Δ
packages/maker/flatpak/src/MakerFlatpak.ts	86.95% <0%> (ø)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update d015bab...fdc176c. Read the comment docs.