cleanup cache on jni unload

Author: madsodgaard

Samples/JExtractJNISampleApp/src/test/java/com/example/swift/VehicleEnumTest.java

@@ -117,7 +117,7 @@ void getAsMotorbike() {
             assertEquals("Yamaha", motorbike.arg0());
             assertEquals(750, motorbike.horsePower());
             assertEquals(OptionalInt.empty(), motorbike.helmets());
-
+            
             vehicle = Vehicle.motorbike("Yamaha", 750, OptionalInt.of(2), arena);
             motorbike = vehicle.getAsMotorbike().orElseThrow();
             assertEquals(OptionalInt.of(2), motorbike.helmets());

Sources/JExtractSwiftLib/JNI/JNISwift2JavaGenerator+SwiftThunkPrinting.swift

@@ -98,6 +98,12 @@ extension JNISwift2JavaGenerator {
       }
     }
 
+    printer.println()
+    printer.print(#"@_cdecl("JNI_OnUnload")"#)
+    printer.printBraceBlock("func JNI_OnUnload(javaVM: UnsafeMutablePointer<JavaVM?>!, reserved: UnsafeMutableRawPointer!)") { printer in
+      printer.print("JNICaches.cleanup()")
+    }
+
     let fileName = "\(self.swiftModuleName)+JNICaches.swift"
 
     if let outputFile = try printer.writeContents(