Generate source maps for releases

Summary:
Allows for optional generation of source maps while building plugins.

Caveat: This will leave a broken `//# sourceMappingURL` comment at the bottom. If you set it to `null`, as the documentation suggests, you will instead get an inlined source map in addition to the written one.

Reviewed By: nikoant

Differential Revision: D29265385

fbshipit-source-id: 1e21e49d2516ecc5909b086e7797736b298b86ab

desktop/scripts/build-plugin.ts

@@ -53,6 +53,11 @@ const argv = yargs
       type: 'string',
       alias: 'ou',
     },
+    'output-sourcemap': {
+      description: 'File path for the sourcemap to be written. Optional.',
+      type: 'string',
+      alias: 'os',
+    },
   })
   .help()
   .strict()
@@ -65,9 +70,10 @@ async function buildPlugin() {
   const outputFileArg = argv.output;
   const outputUnpackedArg = argv['output-unpacked'];
   const minFlipperVersion = argv['min-flipper-version'];
+  const outputSourcemapArg = argv['output-sourcemap'];
   const packageJsonPath = path.join(pluginDir, 'package.json');
   const packageJsonOverridePath = path.join(pluginDir, 'fb', 'package.json');
-  await runBuild(pluginDir, false);
+  await runBuild(pluginDir, false, {sourceMapPath: outputSourcemapArg});
   const checksum = await computePackageChecksum(pluginDir);
   if (previousChecksum !== checksum && argv.version) {
     console.log(`Plugin changed. Packaging new version ${argv.version}...`);