[analyzer] Fix analysis_context_collection_test on Windows

https://dart-review.googlesource.com/c/sdk/+/434802
(0677fcac83) introduced a few new tests
that didn't work on Windows.

Change-Id: I841cb479b6782a83d8472ee4c074ef2b3b51709a
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/435820
Reviewed-by: Johnni Winther <johnniwinther@google.com>
Commit-Queue: Jens Johansen <jensj@google.com>

pkg/analyzer/test/src/dart/analysis/analysis_context_collection_test.dart

@@ -1086,7 +1086,7 @@ workspaces
     var collection = AnalysisContextCollectionImpl(
       resourceProvider: resourceProvider,
       sdkPath: sdkRoot.path,
-      includedPaths: [pubWorkspace.workspaceRootPath],
+      includedPaths: [getFolder(pubWorkspace.workspaceRootPath).path],
     );
 
     // We expect only 1 context.
@@ -1128,9 +1128,9 @@ workspaces
       resourceProvider: resourceProvider,
       sdkPath: sdkRoot.path,
       includedPaths: [
-        pubWorkspace.package1,
-        pubWorkspace.workspaceRootPath,
-        pubWorkspace.package2,
+        getFolder(pubWorkspace.package1).path,
+        getFolder(pubWorkspace.workspaceRootPath).path,
+        getFolder(pubWorkspace.package2).path,
       ],
     );
 
@@ -1198,7 +1198,10 @@ workspaces
     var collection = AnalysisContextCollectionImpl(
       resourceProvider: resourceProvider,
       sdkPath: sdkRoot.path,
-      includedPaths: [pubWorkspace.package1, pubWorkspace.package2],
+      includedPaths: [
+        getFolder(pubWorkspace.package1).path,
+        getFolder(pubWorkspace.package2).path,
+      ],
     );
 
     // We expect only 1 context.