build: add check for lib size

scripts/build/get-dir-size.js

@@ -0,0 +1,32 @@
+// @ts-check
+const { lstatSync, readdirSync } = require("fs");
+const { join } = require("path");
+const { promisify } = require("util");
+const execFile = promisify(require("child_process").execFile);
+
+/**
+ * Find the size of a directory recursively.
+ * Symbolic links are counted once (same inode).
+ * @param {string} root
+ * @param {Set} seen
+ * @returns {number} bytes
+ */
+function getDirSize(root, seen = new Set()) {
+    const stats = lstatSync(root);
+
+    if (seen.has(stats.ino)) {
+        return 0;
+    }
+
+    seen.add(stats.ino);
+
+    if (!stats.isDirectory()) {
+        return stats.size;
+    }
+
+    return readdirSync(root)
+        .map(file => getDirSize(join(root, file), seen))
+        .reduce((acc, num) => acc + num, 0);
+}
+
+exports.getDirSize = getDirSize;