Add riscv64 support for Android NDK projects

[ifarbod]

https://opensource.googleblog.com/2023/10/android-and-risc-v-what-you-need-to-know.html

RISC-V64 is here to stay, NDK can build RISC-V64 applications, so it'd be appropriate for it to be included in Xmake.

You need Android NDK r27c+ to build RISC-V64 projects.

// app/build.gradle.kts
android {
    ndkVersion = "27.2.12479018"
}