better concurrency debugging, --concurrency flag for npx quartz build

quartz/sourcemap.ts

@@ -0,0 +1,19 @@
+import fs from "fs"
+import sourceMapSupport from "source-map-support"
+import { fileURLToPath } from "url"
+
+export const options: sourceMapSupport.Options = {
+  // source map hack to get around query param
+  // import cache busting
+  retrieveSourceMap(source) {
+    if (source.includes(".quartz-cache")) {
+      let realSource = fileURLToPath(source.split("?", 2)[0] + ".map")
+      return {
+        map: fs.readFileSync(realSource, "utf8"),
+      }
+    } else {
+      return null
+    }
+  },
+}
+