Fix build errors with codegen discovery flag enabled

[shwanton]

Please select one of the following

• I am removing an existing difference between facebook/react-native and microsoft/react-native-macos 👍
• I am cherry-picking a change from Facebook's react-native into microsoft/react-native-macos 👍
• I am making a fix / change for the macOS implementation of react-native
• I am making a change required for Microsoft usage of react-native

Summary

Although fabric is not supported on RN Desktop, the codegen aspect of turbomodules should work correctly.

Building RNTester with the USE_CODEGEN_DISCOVERY=1 flag was throwing errors.

build command: USE_CODEGEN_DISCOVERY=1 bundle exec pod install;

[Codegen] Done.
TypeError [ERR_INVALID_ARG_TYPE]: The "args" argument must be of type object. Received type string ('/Users/shawndempsey/src/...)
    at new NodeError (node:internal/errors:372:5)
    at normalizeSpawnArguments (node:child_process:515:11)
    at execFileSync (node:child_process:854:13)
    at /Users/shawndempsey/src/shwanton_react-native-macos/scripts/generate-artifacts.js:238:7
    at Array.forEach (<anonymous>)
    at main (/Users/shawndempsey/src/shwanton_react-native-macos/scripts/generate-artifacts.js:211:15)
    at Object.<anonymous> (/Users/shawndempsey/src/shwanton_react-native-macos/scripts/generate-artifacts.js:322:1)
    at Module._compile (node:internal/modules/cjs/loader:1105:14)
    at Object.Module._extensions..js (node:internal/modules/cjs/loader:1159:10)
    at Module.load (node:internal/modules/cjs/loader:981:32) {
  code: 'ERR_INVALID_ARG_TYPE'
}

There was a change made to generate-artifacts d68d209 that refactored usage to execFileSync. The error is thrown because execFileSync expects an array as it's second argument.

Changelog

[macOS] [Revert] Revert "Use execFileSync over execSync when messing with file paths in generate-artifacts.js"
[macOS] [Fix] Don't try and build Fabric example when USE_CODEGEN_DISCOVERY=1

Test Plan

Build RNTester w/ flag

USE_CODEGEN_DISCOVERY=1 bundle exec pod install

ScreenshotManager Native TurboModule should work from JS

CleanShot.2022-08-02.at.15.37.55-converted.mp4

[Saadnajmi]

@shwanton Do you know if this change would work on RN-macOS 0.68? Considering whether it's worth back porting.

[shwanton]

@Saadnajmi I tested this on the 0.68 branch so will work fine.

[Saadnajmi]

@amgleitman Could you take a second look at this? I worry about the changes of execFileSync -> execSync because security.

[Saadnajmi]

@shwanton execSync is more vulnerable to malformed input moreso than execFileSync, which is why we made the original change. Any chance you can refactor this to use execFileSync?

[shwanton]

Yes, I'll refactor to use execFileSync & call w/ correct args.

[shwanton]

@Saadnajmi Updated to use execFileSync!