This adds basic infrastructure for a stringref implementation in
dart2wasm:
- A `--[no-]stringref` option to the compiler
- An option in the `WasmTarget`, controlling the name of the target
- Separate sets of patch files for the two targets
- Separate platform dill files for the two targets
For now, the patch file contents are the same, and the compiler flag
is not used by the backend (only by the `dart2wasm` script to select
the appropriate platform dill file). Both of these will change as the
implementation progresses.
Tested: ci + manual check that the option selects the correct dill
Change-Id: I2c9bb95ba06fd3de3f7007703ef545e3f0c728ba
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/310621
Commit-Queue: Aske Simon Christensen <askesc@google.com>
Reviewed-by: Ömer Ağacan <omersa@google.com>
