Make package arg to analyzer absolute

Bug: https://github.com/dart-lang/sdk/issues/49646

Change-Id: Ie653b2372ba12992457c25972294c261cb8ea40e
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/254901
Commit-Queue: Michael Thomsen <mit@google.com>
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Reviewed-by: Konstantin Shcheglov <scheglov@google.com>
diff --git a/pkg/dartdev/lib/src/commands/analyze.dart b/pkg/dartdev/lib/src/commands/analyze.dart
index 6237a7a..013be77 100644
--- a/pkg/dartdev/lib/src/commands/analyze.dart
+++ b/pkg/dartdev/lib/src/commands/analyze.dart
@@ -255,7 +255,7 @@
       if (!file.existsSync()) {
         usageException("The file doesn't exist: $path");
       }
-      return file;
+      return file.absolute;
     } else {
       return null;
     }