[dart2wasm] Keep static symbols in dart2wasm-*optimized-* builders

The optimized builders run with binaryen which by default strips static symbols
(in all -Ox modes). So we'll pass `--no-strip-wasm` to `dart compile
wasm` in order to keep the static symbols.

This makes stack traces have the symbols in them which will make tests
that rely on that more likely to work.

Change-Id: I9e0eab8c4ec50ef3a7208551d04a80e9ffa009e8
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/406241
Reviewed-by: Ömer Ağacan <[email protected]>
Commit-Queue: Martin Kustermann <[email protected]>

Author: mkustermann

tools/bots/test_matrix.json

@@ -479,7 +479,8 @@
     "dart2wasm-(linux|mac|win)-optimized-(d8|jsshell|jsc|chrome|firefox)": {
       "options": {
         "dart2wasm-options": [
-          "-O1"
+          "-O1",
+          "--no-strip-wasm"
         ],
         "use-sdk": true,
         "host-asserts": false,