Make 11 test start only on jvm 11+

[Cherry-picked f5dc97f]

Author: rochala

presentation-compiler/test/dotty/tools/pc/tests/completion/CompletionRelease11Suite.scala

@@ -3,13 +3,19 @@ package dotty.tools.pc.tests.completion
 import dotty.tools.pc.base.BaseCompletionSuite
 
 import org.junit.Test
+import org.junit.Before
 import java.nio.file.Path
+import dotty.tools.pc.utils.JRE
 
 class CompletionRelease11Suite extends BaseCompletionSuite:
 
   override protected def scalacOptions(classpath: Seq[Path]): Seq[String] =
     "-release:11" +: super.scalacOptions(classpath)
 
+  @Before
+  def beforeMethod(): Unit =
+    org.junit.Assume.assumeTrue(JRE.getJavaMajorVersion >= 11)
+
   @Test def java11Symbols =
     check(
       """

presentation-compiler/test/dotty/tools/pc/tests/completion/CompletionRelease8Suite.scala

@@ -3,13 +3,19 @@ package dotty.tools.pc.tests.completion
 import dotty.tools.pc.base.BaseCompletionSuite
 
 import org.junit.Test
+import org.junit.Before
 import java.nio.file.Path
+import dotty.tools.pc.utils.JRE
 
 class CompletionRelease8Suite extends BaseCompletionSuite:
 
   override protected def scalacOptions(classpath: Seq[Path]): Seq[String] =
     "-release:8" +: super.scalacOptions(classpath)
 
+  @Before
+  def beforeMethod(): Unit =
+    org.junit.Assume.assumeTrue(JRE.getJavaMajorVersion >= 8)
+
   @Test def noJvm11Symbols =
     check(
       """

presentation-compiler/test/dotty/tools/pc/utils/JRE.scala

@@ -0,0 +1,22 @@
+package dotty.tools.pc.utils
+
+object JRE:
+
+  def getJavaMajorVersion: Int =
+    val javaVersion = sys.env.get("java.version").filter(!_.isEmpty())
+
+    javaVersion match
+      case Some(version) if version.startsWith("1.8") => 8
+      case _ =>
+        scala.util.Try:
+          val versionMethod = classOf[Runtime].getMethod("version")
+          versionMethod.nn.setAccessible(true)
+          val version = versionMethod.nn.invoke(null)
+
+          val majorMethod = version.getClass().getMethod("feature")
+          majorMethod.nn.setAccessible(true)
+          val major = majorMethod.nn.invoke(version).asInstanceOf[Int]
+          major
+        .getOrElse(8) // Minimal version supported by Scala
+
+