fix failing bazel workspace relative path test

pkg/analyzer_cli/test/driver_test.dart

Index: pkg/analyzer_cli/test/driver_test.dart
diff --git a/pkg/analyzer_cli/test/driver_test.dart b/pkg/analyzer_cli/test/driver_test.dart
index 73ee9884acf1ae03ee2d496fc36a7613c7d0ae85..b7a3cdc2ecd29b22e4f7c3318dce8e081f317af0 100644
--- a/pkg/analyzer_cli/test/driver_test.dart
+++ b/pkg/analyzer_cli/test/driver_test.dart
@@ -123,7 +123,7 @@ main() {
         // Copy to temp dir so that existing analysis options
         // in the test directory hierarchy do not interfere
         await withTempDirAsync((String tempDirPath) async {
-          String dartSdkPath = getSdkDir(<String>[])?.path;
+          String dartSdkPath = path.absolute(getSdkDir(<String>[]).path);
           print('>>> dartSdkPath: $dartSdkPath');
           await recursiveCopy(
               new Directory(path.join(testDirectory, 'data', 'bazel')),