sbt-dotty: the binary version is 3 for Scala >= 3.0.0

[smarter]

No description provided.

[adpi2]

Looks good but some tests are failing.

[smarter]

sbt is broken because of sbt/sbt#6422 (which we could work around), mill is broken because of com-lihaoyi/mill#1139

[adpi2]

com-lihaoyi/mill#1139 should be fixed in https://search.maven.org/artifact/com.lihaoyi/mill-main_2.13/0.9.6-16-a5da34/jar

[adpi2]

@smarter could you review this?

[smarter]

Instead of updating DEFAULT_MILL_VERSION in each submodule, could we set MILL_VERSION in the community build runner itself? (this seems like a good idea in general, in the same way that we use a single sbt version for the whole community build). I haven't checked but a change like this should work:

diff --git community-build/src/scala/dotty/communitybuild/projects.scala community-build/src/scala/dotty/communitybuild/projects.scala
index 755f774449f..c32a3ed6839 100644
--- community-build/src/scala/dotty/communitybuild/projects.scala
+++ community-build/src/scala/dotty/communitybuild/projects.scala
@@ -25,6 +25,7 @@ def exec(projectDir: Path, binary: String, arguments: String*): Int =
   val command = binary +: arguments
   log(command.mkString(" "))
   val builder = new ProcessBuilder(command: _*).directory(projectDir.toFile).inheritIO()
+  builder.environment.put("MILL_VERSION", "0.9.6-16-a5da34")
   val process = builder.start()
   val exitCode = process.waitFor()
   exitCode

[smarter]

Thanks for the help!