Downgrade sbt to 1.12.1 (was 1.12.10) (#25995)

Workaround for sbt/sbt#9185.
As suggested in
#25973 (comment).

Author: mbovel

community-build/src/scala/dotty/communitybuild/projects.scala

@@ -117,7 +117,7 @@ final case class SbtCommunityProject(
     val sbtProps = Option(System.getProperty("sbt.ivy.home")) match
       case Some(ivyHome) => List(s"-Dsbt.ivy.home=$ivyHome")
       case _ => Nil
-    extraSbtArgs ++ sbtProps ++ List("-sbt-version", "1.12.9", "-Dsbt.supershell=false", s"--addPluginSbtFile=$sbtPluginFilePath")
+    extraSbtArgs ++ sbtProps ++ List("-sbt-version", "1.12.1", "-Dsbt.supershell=false", s"--addPluginSbtFile=$sbtPluginFilePath")
 
 object SbtCommunityProject:
   def scalacOptions = List(

project/build.properties

@@ -1 +1 @@
-sbt.version=1.12.10
+sbt.version=1.12.1