Don't run bootstrapped tests with java 11

And revert changes to staging test

The dotty-staging handling of classpath does not work with Java 11.
Two bootstrap-only tests sepcific to staging failed.

(1) Failure in `project/scripts/bootstrapCmdTests`

+ ./project/scripts/sbt ';dotty-compiler-bootstrapped/dotc -with-compiler tests/run-staging/quote-run.scala; dotty-compiler-bootstrapped/dotr -with-compiler Test'
Exception in thread "main" dotty.tools.dotc.MissingCoreLibraryException: Could not find package scalaShadowing from compiler core libraries.
Make sure the compiler core libraries are on the classpath.

  at dotty.tools.dotc.core.Denotations$.select$1(Denotations.scala:1222)
  at dotty.tools.dotc.core.Denotations$.recurSimple$1(Denotations.scala:1250)
  at dotty.tools.dotc.core.Denotations$.recur$1(Denotations.scala:1252)
  at dotty.tools.dotc.core.Denotations$.staticRef(Denotations.scala:1254)
  at dotty.tools.dotc.core.Symbols$.requiredPackage(Symbols.scala:890)
  at dotty.tools.dotc.core.Definitions.ScalaShadowingPackage(Definitions.scala:255)
  at dotty.tools.dotc.core.Definitions.init(Definitions.scala:1496)
  at dotty.tools.dotc.core.Contexts$ContextBase.initialize(Contexts.scala:790)
  at dotty.tools.dotc.core.Contexts$Context.initialize(Contexts.scala:554)
  at dotty.tools.dotc.Run.rootContext(Run.scala:64)
  at dotty.tools.dotc.Run.<init>(Run.scala:84)
  at scala.quoted.staging.QuoteCompiler$ExprRun.<init>(QuoteCompiler.scala:102)
  at scala.quoted.staging.QuoteCompiler.newRun(QuoteCompiler.scala:45)
  at scala.quoted.staging.QuoteDriver.run(QuoteDriver.scala:40)
  at scala.quoted.staging.Toolbox$$anon$1.run(Toolbox.scala:36)
  at scala.quoted.staging.package$.run(staging.scala:19)
  at Test$.main(quote-run.scala:12)
  at Test.main(quote-run.scala)

(2) tests/run-staging/i6992

-- Error: tests/run-staging/i6992/Test_2.scala:7:16 -------------------------------
7 |    println(mcr {foo})
  |            ^^^^^^^^^
  | Exception occurred while executing macro expansion.
  | dotty.tools.dotc.MissingCoreLibraryException: Could not find package scalaShadowing from compiler core libraries.
  | Make sure the compiler core libraries are on the classpath.

Author: liufengyun

.github/workflows/ci.yaml

@@ -58,9 +58,6 @@ jobs:
     container: lampepfl/dotty:2020-04-24
 
     steps:
-      - name: Set up JDK version
-        run: echo "::add-path::/usr/lib/jvm/java-11-openjdk-amd64/bin"
-
       - name: Checkout cleanup script
         uses: actions/checkout@v2
 

tests/run-staging/i6992/Macro_1.scala

@@ -2,7 +2,7 @@
 import scala.quoted._
 import scala.quoted.staging._
 
-// given Toolbox = Toolbox.make(getClass.getClassLoader)
+given Toolbox = Toolbox.make(getClass.getClassLoader)
 
 object macros {
   inline def mcr(x: => Any): Any = ${mcrImpl('x)}
@@ -13,7 +13,7 @@ object macros {
     import ctx.tasty._
     try {
       body match {
-        case '{$x: Foo} => x // Expr(run(x).x)
+        case '{$x: Foo} => Expr(run(x).x)
       }
     } catch {
       case ex: scala.quoted.ScopeException =>