Run dex checker only on java 6 files

compiler/tests-common/org/jetbrains/kotlin/codegen/DxChecker.java

@@ -23,10 +23,10 @@ import com.android.dx.dex.cf.CfTranslator;
 import com.android.dx.dex.file.DexFile;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.kotlin.backend.common.output.OutputFile;
+import org.jetbrains.org.objectweb.asm.Opcodes;
 import org.junit.Assert;
 
-import java.io.PrintWriter;
-import java.io.StringWriter;
+import java.io.*;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 
@@ -47,7 +47,9 @@ public class DxChecker {
         for (OutputFile file : ClassFileUtilsKt.getClassFiles(outputFiles)) {
             try {
                 byte[] bytes = file.asByteArray();
-                checkFileWithDx(bytes, file.getRelativePath(), arguments);
+                if (isJava6Class(bytes)) {
+                    checkFileWithDx(bytes, file.getRelativePath(), arguments);
+                }
             }
             catch (Throwable e) {
                 Assert.fail(generateExceptionMessage(e));
@@ -55,6 +57,18 @@ public class DxChecker {
         }
     }
 
+    private static boolean isJava6Class(byte[] bytes) throws IOException {
+        try (DataInputStream stream = new DataInputStream(new ByteArrayInputStream(bytes))) {
+            int header = stream.readInt();
+            if (0xCAFEBABE != header) {
+                throw new IOException("Invalid header class header: " + header);
+            }
+            int minor = stream.readUnsignedShort();
+            int major = stream.readUnsignedShort();
+            return major == Opcodes.V1_6;
+        }
+    }
+
     public static void checkFileWithDx(byte[] bytes, @NotNull String relativePath) {
         Main.Arguments arguments = new Main.Arguments();
         String[] array = new String[1];