[Breaking Change] Use the real main queue with Johnno's toolchain

This should be temporary until we get the libdispatch build working again.

Author: ephemer

Sources/JNI/SwiftJNI.swift

@@ -12,6 +12,7 @@ public func JNI_OnLoad(jvm: UnsafeMutablePointer<JavaVM>, reserved: UnsafeMutabl
     jni = localJNI // set the global for use elsewhere
 
     #if os(Android)
+    DispatchQueue.drainingMainQueue = true
     DispatchQueue.setThreadDetachCallback(JNI_DetachCurrentThread)
     #endif