Run original small subset of tests on Appveyor

Author: liufengyun

.appveyor.yml

@@ -14,7 +14,7 @@ init:
 build_script:
   - cmd: sbt dotty-bootstrapped/compile
 test_script:
-  # - cmd: sbt "dotty-bootstrapped/dotc tests\pos\HelloWorld.scala"
+  - cmd: sbt "dotty-bootstrapped/dotc tests\pos\HelloWorld.scala"
   # - cmd: sbt test
-  - cmd: sbt dotty-bootstrapped/test
-  # - cmd: sbt sjsJUnitTests/test
+  # - cmd: sbt dotty-bootstrapped/test
+  - cmd: sbt sjsJUnitTests/test