Merge: Fix C compiler warning on Java FFI and Android apps

The generated C code used `static JNIEXPORT`, when the macro was expanded it duplicated the visibility attribute. It was reported by the C compiler as a warning. This PR removes the `static` part.

Pull-Request: #1327
Reviewed-by: Jean Privat <jean@pryen.org>
Reviewed-by: Romain Chanoir <chanoir.romain@courrier.uqam.ca>