Fix task macro's handling of Symbol owners in <qual>.value

The qualifier of the `.value` call may contain `DefTree`s (e.g.
vals, defs) or `Function` trees. When we snip them out of the
tree and graft them into a new context, we must also call
`changeOwner`, so that the symbol owner structure and the tree
structure are coherent.

Failure to do so resulted in a crash in the compiler backend.

Fixes #1150

sbt/src/sbt-test/project/setting-macro/build.sbt

@@ -15,3 +15,15 @@ demo := {
   val (n, s) = parser.parsed
   s * n
 }
+
+// Tests for correct Symbol owner structure in the lifted qualifiers of
+// the `.value` macro within a task macro. (#1150)
+val key1 = taskKey[Unit]("")
+
+key1 := {
+  val foo = (sourceDirectory in Compile).apply(base => base).value.get
+	testFrameworks.value.flatMap(f =>
+		None.map(_ => f)
+	)
+  ()
+}

util/appmacro/src/main/scala/sbt/appmacro/ContextUtil.scala

@@ -226,17 +226,20 @@ final class ContextUtil[C <: Context](val ctx: C)
 		object appTransformer extends Transformer
 		{
 			override def transform(tree: Tree): Tree =
-				tree match
-				{
-					case ApplyTree(TypeApply(Select(_, nme), targ :: Nil), qual :: Nil) => subWrapper(nme.decoded, targ.tpe, qual, tree) match {
-						case Converted.Success(t, finalTx) => finalTx(t)
+				tree match {
+					case ApplyTree(TypeApply(Select(_, nme), targ :: Nil), qual :: Nil) =>
+						subWrapper(nme.decoded, targ.tpe, qual, tree) match {
+							case Converted.Success(t, finalTx) =>
+								changeOwner(qual, currentOwner, initialOwner) // Fixes https://github.com/sbt/sbt/issues/1150
+								finalTx(t)
 							case Converted.Failure(p,m) => ctx.abort(p, m)
 							case _: Converted.NotApplicable[_] => super.transform(tree)
 						}
 					case _ => super.transform(tree)
 				}
 		}
-
+		appTransformer.atOwner(initialOwner) {
 			appTransformer.transform(t)
 		}
 	}
+}