Support for RISC-V 64-bit GNU/Linux

Author: msizanoen1

ci/build.sh

@@ -220,6 +220,7 @@ nvptx64-nvidia-cuda \
 powerpc-unknown-linux-gnuspe \
 powerpc-unknown-netbsd \
 powerpc64-unknown-freebsd \
+riscv64gc-unknown-linux-gnu \
 riscv32imac-unknown-none-elf \
 riscv32imc-unknown-none-elf \
 sparc64-unknown-netbsd \

src/unix/linux_like/linux/gnu/b64/mod.rs

@@ -78,6 +78,9 @@ cfg_if! {
     } else if #[cfg(any(target_arch = "x86_64"))] {
         mod x86_64;
         pub use self::x86_64::*;
+    } else if #[cfg(any(target_arch = "riscv64"))] {
+        mod riscv64;
+        pub use self::riscv64::*;
     } else {
         // Unknown target_arch
     }