Function bdk_chain::bitcoin::secp256k1::ffi::secp256k1_schnorrsig_sign
pub unsafe extern "C" fn secp256k1_schnorrsig_sign(
cx: *const Context,
sig: *mut u8,
msg32: *const u8,
keypair: *const Keypair,
aux_rand32: *const u8
) -> i32