Only use StackFrameClassWriter where required

Java 11's Pack200 implementation complains if stack map frames are present, and
passes the classes through unmodified. I'm not sure why.

Stack map frames are only required in Java 7, so for 6 and below a reasonable
workaround is to not emit them.

A nice side effect of this change is that the jar files created by the bundler
are be smaller. The pack200 files are too, and would be even if the classes
were not passed through unmodified.

asm/src/main/java/dev/openrs2/asm/classpath/Library.kt

@@ -1,12 +1,15 @@
 package dev.openrs2.asm.classpath
 
 import com.github.michaelbull.logging.InlineLogger
+import dev.openrs2.asm.ClassVersionUtils
 import dev.openrs2.asm.NopClassVisitor
 import dev.openrs2.asm.remap
 import dev.openrs2.compress.gzip.Gzip
 import dev.openrs2.crypto.Pkcs12KeyStore
 import dev.openrs2.util.io.DeterministicJarOutputStream
 import org.objectweb.asm.ClassReader
+import org.objectweb.asm.ClassWriter
+import org.objectweb.asm.Opcodes
 import org.objectweb.asm.commons.Remapper
 import org.objectweb.asm.tree.ClassNode
 import org.objectweb.asm.util.CheckClassAdapter
@@ -70,7 +73,11 @@ class Library constructor() : Iterable<ClassNode> {
     fun writeJar(classPath: ClassPath, out: OutputStream, manifest: Manifest? = null) {
         DeterministicJarOutputStream.create(out, manifest).use { jar ->
             for (clazz in classes.values) {
-                val writer = StackFrameClassWriter(classPath)
+                val writer = if (ClassVersionUtils.gte(clazz.version, Opcodes.V1_7)) {
+                    StackFrameClassWriter(classPath)
+                } else {
+                    ClassWriter(ClassWriter.COMPUTE_MAXS)
+                }
 
                 clazz.accept(writer)