[vm] Make `iso-stress` builder use valid -Dtest_configuration when compiling the giant stress test

Some tests that are run as part of the giant iso-stress test are relying
on `package:expect/config.config` getters, which in return rely on the
test configuration being set as part of the compilation from the app

=> We pass valid JIT & AOT configurations when compiling the giant iso
   stress test files.

TEST=May fix the iso-stress failures.

Change-Id: Icacbfe941eb01030c010670f35848a76c9a8ee12
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/353102
Reviewed-by: Daco Harkes <dacoharkes@google.com>
Commit-Queue: Martin Kustermann <kustermann@google.com>
diff --git a/tools/bots/test_matrix.json b/tools/bots/test_matrix.json
index cc0cdbe..2820882 100644
--- a/tools/bots/test_matrix.json
+++ b/tools/bots/test_matrix.json
@@ -3435,6 +3435,7 @@
             "pkg/vm/bin/gen_kernel.dart",
             "--platform=out/ReleaseX64/vm_platform_strong.dill",
             "--no-aot",
+            "-Dtest_runner.configuration=vm-linux-release-x64",
             "-o",
             "runtime/tests/concurrency/generated_stress_test.dart.jit.dill",
             "runtime/tests/concurrency/generated_stress_test.dart"
@@ -3447,6 +3448,7 @@
             "pkg/vm/bin/gen_kernel.dart",
             "--platform=out/ReleaseX64/vm_platform_strong.dill",
             "--aot",
+            "-Dtest_runner.configuration=vm-aot-linux-release-x64",
             "-o",
             "runtime/tests/concurrency/generated_stress_test.dart.aot.dill",
             "runtime/tests/concurrency/generated_stress_test.dart"