Move legacy assert tests to launcher

since they are broken on JDK 11: they change Field.modifiers, which is prohibited
since JDK 9, because this private field is not exported.
Thus, we need to split the test into two: one with assertions enabled and the other
one with them disabled. Also, we need to run them in separate processes, for them
not to interfere each other.
 #KT-27176 Fixed

compiler/tests/org/jetbrains/kotlin/cli/LauncherScriptTest.kt

@@ -161,4 +161,20 @@ class LauncherScriptTest : TestCaseWithTmpdir() {
             expectedStdout = "a, b, 4, 2\n"
         )
     }
+
+    fun testLegacyAssert() {
+        runProcess(
+            "kotlinc",
+            "$testDataDirectory/legacyAssertDisabled.kt", "-Xassertions=legacy", "-d", tmpdir.path
+        )
+
+        runProcess("kotlin", "LegacyAssertDisabledKt", "-J-da:kotlin._Assertions", workDirectory = tmpdir)
+
+        runProcess(
+            "kotlinc",
+            "$testDataDirectory/legacyAssertEnabled.kt", "-Xassertions=legacy", "-d", tmpdir.path
+        )
+
+        runProcess("kotlin", "LegacyAssertEnabledKt", "-J-ea:kotlin._Assertions", workDirectory = tmpdir)
+    }
 }