Account for file URLs vs file paths

A case where we encounter this is not known.
Only saw this while stepping through Node.js internals.

packages/next/src/server/patch-error-inspect.ts

@@ -141,7 +141,14 @@ function getSourcemappedFrameIfPossible(
   let sourceMap: SyncSourceMapConsumer
   let sourceMapPayload: ModernSourceMapPayload
   if (sourceMapCacheEntry === undefined) {
-    const moduleSourceMap = findSourceMap(frame.file)
+    let sourceURL = frame.file
+    // e.g. "/APP/.next/server/chunks/ssr/[root of the server]__2934a0._.js"
+    // will be keyed by Node.js as "file:///APP/.next/server/chunks/ssr/[root%20of%20the%20server]__2934a0._.js".
+    // This is likely caused by `callsite.toString()` in `Error.prepareStackTrace converting file URLs to paths.
+    if (sourceURL.startsWith('/')) {
+      sourceURL = url.pathToFileURL(frame.file).toString()
+    }
+    const moduleSourceMap = findSourceMap(sourceURL)
     if (moduleSourceMap === undefined) {
       return null
     }