Improve dead code detection (#22829)

scripts/analyse_unused_exports.js

@@ -4,15 +4,21 @@
 const fs = require("fs");
 const { exec } = require("node:child_process");
 
+const includeJSSDK = process.argv.includes("--include-js-sdk");
 const ignore = [];
 
 ignore.push(...Object.values(JSON.parse(fs.readFileSync(`${__dirname}/../components.json`))));
 ignore.push("/index.ts");
+// We ignore js-sdk by default as it may export for other non element-web projects
+if (!includeJSSDK) ignore.push("matrix-js-sdk");
 
 const command = `yarn ts-prune --ignore "${ignore.join("|")}" | grep -v "(used in module)"`;
 
-exec(command, (error, stdout) => {
+exec(command, (error, stdout, stderr) => {
     if (error) throw error;
+    // We have to do this as piping the output of ts-prune causes the return
+    // code to be 0
+    if (stderr) throw Error(stderr);
 
     let lines = stdout.split("\n");
     // Remove the first line as that is the command that was being run and we