use riscv crate from github

Author: wangrunji0408

crate/riscv

@@ -48,7 +48,7 @@ uart_16550 = "0.1"
 pc-keyboard = "0.3"
 
 [target.'cfg(any(target_arch = "riscv32", target_arch = "riscv64"))'.dependencies]
-riscv = { path = "../crate/riscv" }
+riscv = { git = "https://github.com/riscv-and-rust-and-decaf/riscv" }
 bbl = { path = "../crate/bbl" }
 
 [target.'cfg(target_arch = "aarch64")'.dependencies]

kernel/Cargo.lock

@@ -454,7 +454,7 @@ fi
 CNAME=riscv
 if ! [[ -f outdir/${CNAME}.o ]]
 then
-rustc --crate-name riscv ../crate/riscv/src/lib.rs \
+rustc --crate-name riscv $CARGO_PATH/git/checkouts/riscv-1e845b622ce46f1d/f7bea54*/src/lib.rs \
  --color always --crate-type lib --emit=metadata,llvm-bc \
  -C opt-level=1 \
  -C debuginfo=2 \