test: enable runfiles tree on Windows for e2e/bzlmod (#2886)

### Changes are visible to end-users: no

### Test plan

- Covered by existing test cases

e2e/bzlmod/.bazelrc

diff --git a/e2e/bzlmod/.bazelrc b/e2e/bzlmod/.bazelrc
index 58d7130..8c86f24 100644
--- a/e2e/bzlmod/.bazelrc
+++ b/e2e/bzlmod/.bazelrc
@@ -1,2 +1,6 @@
 import %workspace%/../../tools/preset.bazelrc
 import %workspace%/../e2e.bazelrc
+
+# Materialize the runfiles tree on Windows (default elsewhere) so tests can read
+# data files via relative paths.
+common:windows --enable_runfiles