Disable some flaky scalatest's tests

We usually don't notice these failures because the community build
retries a project up to three times in case of failure, but sometimes
all three of them fail, and even when it succeeds it means that
community_build_a sometimes takes much longer than it needs to (2 hours
instead of 1 hour).

I'v reported this upstream at
scalatest/scalatest#2049.

community-build/src/scala/dotty/communitybuild/projects.scala

@@ -278,7 +278,19 @@ object projects:
 
   lazy val scalatest: SbtCommunityProject = SbtCommunityProject(
     project       = "scalatest",
-    sbtTestCommand   = "scalacticDotty/clean; scalacticDottyJS/clean; scalacticTestDotty/test; scalatestTestDotty/test; scalacticDottyJS/compile; scalatestDottyJS/compile",
+    sbtTestCommand   =
+      List(
+        "scalacticDotty/clean; scalacticDottyJS/clean",
+
+        // Some scalatest's tests are flaky (https://github.com/scalatest/scalatest/issues/2049)
+        // so we disable them, this list is based on the one used in the Scala 2 community build
+        // (https://github.com/scala/community-build/blob/2.13.x/proj/scalatest.conf).
+        """set scalatestTest / Test / unmanagedSources / excludeFilter := HiddenFileFilter || "GeneratorSpec.scala" || "FrameworkSuite.scala" || "WaitersSpec.scala" || "TestSortingReporterSpec.scala" || "JavaFuturesSpec.scala" || "ParallelTestExecutionSpec.scala" || "TimeLimitsSpec.scala" || "TestThreadsStartingCounterSpec.scala" || "SuiteSortingReporterSpec.scala" || "CommonGeneratorsSpec.scala" || "PropCheckerAssertingSpec.scala" || "ConductorMethodsSuite.scala"""",
+        """set scalacticTest / Test / unmanagedSources / excludeFilter := HiddenFileFilter || "NonEmptyArraySpec.scala"""",
+        """set genRegularTests4 / Test / managedSources ~= (_.filterNot(_.getName == "FrameworkSuite.scala").filterNot(_.getName == "GeneratorSpec.scala").filterNot(_.getName == "CommonGeneratorsSpec.scala").filterNot(_.getName == "ParallelTestExecutionSpec.scala").filterNot(_.getName == "DispatchReporterSpec.scala").filterNot(_.getName == "TestThreadsStartingCounterSpec.scala").filterNot(_.getName == "EventuallySpec.scala"))""",
+
+        "scalacticTestDotty/test; scalatestTestDotty/test; scalacticDottyJS/compile; scalatestDottyJS/compile"
+      ).mkString("; "),
     sbtPublishCommand = "scalacticDotty/publishLocal; scalatestDotty/publishLocal; scalacticDottyJS/publishLocal; scalatestDottyJS/publishLocal",
     sbtDocCommand = ";scalacticDotty/doc", // fails with missing type ;scalatestDotty/doc"
     // cannot take signature of (test: org.scalatest.concurrent.ConductorFixture#OneArgTest):