app: fix cgo exported function signature
app: fix cgo exported function signature

Fixes a build warning:

android.c:102:44: warning: incompatible pointer types assigning to 'void (*)(ANativeActivity *, int)' (aka 'void (*)(struct ANativeActivity *, int)') from 'void (ANativeActivity *, GoInt)' (aka 'void (struct ANativeActivity *, long long)') [-Wincompatible-pointer-types]

Change-Id: Ib70bcf8a8e32bb1885ec809d239199fccb1dc4fa
Reviewed-on: https://go-review.googlesource.com/128235
Reviewed-by: Hyang-Ah Hana Kim <d7e82c3c07f92613bcbf9a1e88f6b96c13caa3b0@gmail.com>

golang/mobile,golang/mobile,golang/mobile,golang/mobile