Use Wconf to silence Unsafe usage under jdk18

Author: som-snytt

compiler/src/dotty/tools/dotc/profile/Profiler.scala

@@ -1,5 +1,6 @@
 package dotty.tools.dotc.profile
 
+import scala.annotation.*
 import scala.language.unsafeNulls
 
 import java.io.{FileWriter, PrintWriter}
@@ -123,6 +124,7 @@ private [profile] class RealProfiler(reporter : ProfileReporter)(using Context)
   }
   private def readHeapUsage() = RealProfiler.memoryMx.getHeapMemoryUsage.getUsed
 
+  @nowarn
   private def doGC: Unit = {
     System.gc()
     System.runFinalization()

project/Build.scala

@@ -169,9 +169,10 @@ object Build {
       "-feature",
       "-deprecation",
       "-unchecked",
-      "-Xfatal-warnings",
+      "-Wconf:cat=deprecation&msg=Unsafe:s",
+      "-Werror",
       "-encoding", "UTF8",
-      "-language:implicitConversions"
+      "-language:implicitConversions",
     ),
 
     (Compile / compile / javacOptions) ++= Seq("-Xlint:unchecked", "-Xlint:deprecation"),