[native] Revert D4717

Summary:
There were some changes I made in D4717 that appear to have broken running yarn react-native run-android when trying to build and run the Android app. I encountered this issue when fixing ENG-1485. The yarn react-native run-android command would fail with an error that went away once the changes in this diff were reverted.

I've also added the necessary ShellCheck directives to this file (for the time being, until I can figure out how to clean up this file correctly) so that the ShellCheck CI/GitHub Actions still passes. The Linear issue for fixing this file correctly is here.

Test Plan:
After incorporating these changes, running:

cd keyserver && yarn dev

in one terminal,

cd native && yarn dev

in another terminal, and

yarn react-native run-android

in another terminal passes with no errors and builds the Android app correctly. However, without this reversion, yarn react-native run-android fails.

Reviewers: atul, tomek, jon, karol, ashoat

Reviewed By: ashoat

Subscribers: ashoat, adrian

Differential Revision: https://phab.comm.dev/D4759