Can't add sbt-spiewak projects to the Scala 3 community build

[armanbilge]

This is because the isDotty setting added to sbt-spiewak in #54 conflicts with the one in the DottyPlugin used in the community build:

/__w/dotty/dotty/community-build/community-projects/http4s/build.sbt:1059: error: reference to isDotty is ambiguous;
it is imported twice in the same scope by
import _root_.sbtspiewak.SpiewakPlugin.autoImport._
and import _root_.dotty.tools.sbtplugin.DottyPlugin.autoImport._
    if (isDotty.value && githubIsWorkflowBuild.value)

Currently, all the projects in the CB using sbt-spiewak are using an old version of the plugin. But this means they cannot be updated.

I've asked in scala/scala3#14071 (comment) if the DottyPlugin is still needed since it was merged into sbt. However, is the isDotty setting still necessary for sbt-spiewak? According to sbt/sbt#6080 isDotty has been renamed to isScala3 in sbt.

[armanbilge]

Hmm, seems isScala3 didn't make it into sbt after all based on sbt/sbt#6080 (comment). So maybe we can rename isDotty in sbt-spiewak to isScala3.

[armanbilge]

They are removing sbt-dotty from the Community Build in scala/scala3#14395.