[K/JS] Add a secret system property to enable the old Kotlin/JS compiler only for tests until it will be removed from the sources

compiler/tests-common/tests/org/jetbrains/kotlin/cli/AbstractCliTest.java

@@ -286,13 +286,20 @@ public abstract class AbstractCliTest extends TestCaseWithTmpdir {
     }
 
     protected void doJsTest(@NotNull String fileName) {
+        setupOldJsCompiler(fileName);
         doTest(fileName, new K2JSCompiler());
     }
 
     protected void doJsDceTest(@NotNull String fileName) {
+        setupOldJsCompiler(fileName);
         doTest(fileName, new K2JSDce());
     }
 
+    private void setupOldJsCompiler(String fileName) {
+        if (fileName == null) return;
+        CompilerSystemProperties.KOTLIN_JS_COMPILER_LEGACY_FORCE_ENABLED.setValue(Boolean.toString(!fileName.contains("_strict")));
+    }
+
     protected void doMetadataTest(@NotNull String fileName) {
         doTest(fileName, new K2MetadataCompiler());
     }

compiler/tests-common/tests/org/jetbrains/kotlin/jvm/compiler/AbstractKotlinCompilerIntegrationTest.kt

@@ -20,6 +20,7 @@ import com.intellij.openapi.util.io.FileUtil
 import com.intellij.util.io.ZipUtil
 import org.jetbrains.kotlin.cli.AbstractCliTest
 import org.jetbrains.kotlin.cli.common.CLICompiler
+import org.jetbrains.kotlin.cli.common.CompilerSystemProperties
 import org.jetbrains.kotlin.cli.common.ExitCode
 import org.jetbrains.kotlin.cli.js.K2JSCompiler
 import org.jetbrains.kotlin.cli.jvm.K2JVMCompiler
@@ -167,6 +168,8 @@ abstract class AbstractKotlinCompilerIntegrationTest : TestCaseWithTmpdir() {
             args.add("-output")
             args.add(output.path)
             args.add("-meta-info")
+            // TODO: It will be deleted after all of our internal vendors will use the new Kotlin/JS compiler
+            CompilerSystemProperties.KOTLIN_JS_COMPILER_LEGACY_FORCE_ENABLED.value = "true"
         } else if (compiler is K2JVMCompiler || compiler is K2MetadataCompiler) {
             if (classpath.isNotEmpty()) {
                 args.add("-classpath")