bugfix: consider TS' target in call to parseRuntime()

[nettybun]

Closes #2628

Currently esbuild emits ||= even when TS target is set to ES6:

$ echo 'var a = { a:1 }; window.xyz ||= a; export default { b:2, ...a }' | ./esbuild --loader=ts --tsconfig-raw='{"compilerOptions": { "target": "es6" }}'
[...]
var __spreadValues = (a2, b) => {
  for (var prop in b ||= {})
    [...]
  return a2;
};
var a = { a: 1 };
window.xyz || (window.xyz = a);
export default __spreadValues({ b: 2 }, a);

This PR fixes the output to lower ||= into b || (b = {}):

$ echo 'var a = { a:1 }; window.xyz ||= a; export default { b:2, ...a }' | ./esbuild --loader=ts --tsconfig-raw='{"compilerOptions": { "target": "es6" }}'
[...]
var __spreadValues = (a2, b) => {
  for (var prop in b || (b = {}))
   [...]
  return a2;
};
var a = { a: 1 };
window.xyz || (window.xyz = a);
export default __spreadValues({ b: 2 }, a);

Disclaimer: I've never written Go and I debugged this with a dozen fmt.Println() calls. Sorry I'm not up for writing tests. Also see PR comment about the cache key.

[nettybun]

Please review/edit this line - I'll defer to you on whether an ES version number like 2015 is more appropriate than a pointer.

[nettybun]

@evanw Is this ok to be merged? My company is patching esbuild to workaround it but would prefer official upstream release. Thank you! 👏

[evanw]

I’m closing this PR as #2628 has been closed. The target field of tsconfig.json no longer affects esbuild’s syntax transforms.