Fix checks running in clones with nonstandard names (#5960)

Author: wilhuff

scripts/check_imports.swift

@@ -145,7 +145,11 @@ private func main() -> Int32 {
   let logger = ErrorLogger()
   // Search the path upwards to find the root of the firebase-ios-sdk repo.
   var url = URL(fileURLWithPath: FileManager().currentDirectoryPath)
-  while url.path != "/", url.lastPathComponent != "firebase-ios-sdk" {
+  while url.path != "/" {
+    let script = url.appendingPathComponent("scripts/check_imports.swift")
+    if FileManager.default.fileExists(atPath: script.path) {
+      break
+    }
     url = url.deletingLastPathComponent()
   }
   let repoURL = url