[ddc] emit full dill as part of modular tests.
[ddc] emit full dill as part of modular tests.

This small change brings the modular test closer to the behavior we have
internally in our bazel rules.

Turns out that recently we discovered a bug in the static erasure
transformation when emitting the full dill generated by DDC. This change
will allow us to detect these kind of failures in our SDK repo as well.

Change-Id: I9032d2563f741692ae03035b9fc9be59ab4b3a38
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/247761
Reviewed-by: Srujan Gaddam <4175f2f2dd3cde6c8ffb10fc9674dc09abf813fe@google.com>
Commit-Queue: Sigmund Cherem <beaea8fd7d2a56555046ba4f362c8a93e3938576@google.com>
Reviewed-by: Nicholas Shahan <03847abd2d8aadfe859ecb98095a31f9f515dc47@google.com>

dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk