set baseline java version to 17 (Netflix-Skunkworks#397)

In preparation for Spring 6, drop support for jdk8 and jdk11.

project/BuildSettings.scala

@@ -7,9 +7,8 @@ object BuildSettings {
     "-deprecation",
     "-unchecked",
     "-Xlint:_,-infer-any",
-    "-feature")
-
-  private val isRecentJdk = System.getProperty("java.specification.version").toDouble >= 11.0
+    "-feature",
+    "-release", "17")
 
   lazy val checkLicenseHeaders = taskKey[Unit]("Check the license headers for all source files.")
   lazy val formatLicenseHeaders = taskKey[Unit]("Fix the license headers for all source files.")
@@ -19,20 +18,8 @@ object BuildSettings {
   lazy val buildSettings = baseSettings ++ Seq(
     organization := "com.netflix.iep-apps",
     scalaVersion := Dependencies.Versions.scala,
-    scalacOptions ++= {
-      // -release option is not supported in scala 2.11
-      val v = scalaVersion.value
-      CrossVersion.partialVersion(v).map(_._2.toInt) match {
-        case Some(v) if v > 11 && isRecentJdk => compilerFlags ++ Seq("-release", "8")
-        case _                                => compilerFlags ++ Seq("-target:jvm-1.8")
-      }
-    },
-    javacOptions ++= {
-      if (isRecentJdk)
-        Seq("--release", "8")
-      else
-        Seq("-source", "1.8", "-target", "1.8")
-    },
+    scalacOptions ++= compilerFlags,
+    javacOptions ++= Seq("--release", "17"),
     crossPaths := true,
     crossScalaVersions := Dependencies.Versions.crossScala,
     sourcesInBase := false,