Use the same compilation flags in non-bootstrapped and bootstrapped builds

This avoids finding compilation errors late in the development cycle. Having
explicit nulls on is especially important because typed and untyped trees are
now only distinguished using `Null`, so on the non-bootstrapped build we don't
get compiler errors when passing an untyped Tree where a typed Tree is expected.

Author: smarter

project/Build.scala

@@ -526,6 +526,9 @@ object Build {
 
   // Settings shared between scala3-compiler and scala3-compiler-bootstrapped
   lazy val commonDottyCompilerSettings = Seq(
+       // Note: bench/profiles/projects.yml should be updated accordingly.
+       Compile / scalacOptions ++= Seq("-Yexplicit-nulls", "-Ysafe-init"),
+
       // Generate compiler.properties, used by sbt
       (Compile / resourceGenerators) += Def.task {
         import java.util._
@@ -804,9 +807,6 @@ object Build {
       )
     },
 
-    // Note: bench/profiles/projects.yml should be updated accordingly.
-    Compile / scalacOptions ++= Seq("-Yexplicit-nulls", "-Ysafe-init"),
-
     repl := (Compile / console).value,
     Compile / console / scalacOptions := Nil, // reset so that we get stock REPL behaviour!  E.g. avoid -unchecked being enabled
   )