support riscv64 target

Signed-off-by: xermicus <cyrill@parity.io>

crates/llvm-context/src/target_machine/target.rs

@@ -13,14 +13,20 @@ impl Target {
     /// Returns the target name.
     pub fn name(&self) -> &str {
         match self {
+            #[cfg(not(feature = "riscv-64"))]
             Self::PVM => "riscv32",
+            #[cfg(feature = "riscv-64")]
+            Self::PVM => "riscv64",
         }
     }
 
     /// Returns the target triple.
     pub fn triple(&self) -> &str {
         match self {
+            #[cfg(not(feature = "riscv-64"))]
             Self::PVM => "riscv32-unknown-unknown-elf",
+            #[cfg(feature = "riscv-64")]
+            Self::PVM => "riscv64-unknown-unknown-elf",
         }
     }
 
@@ -37,7 +43,10 @@ impl FromStr for Target {
 
     fn from_str(string: &str) -> Result<Self, Self::Err> {
         match string {
+            #[cfg(not(feature = "riscv-64"))]
             "riscv32" => Ok(Self::PVM),
+            #[cfg(feature = "riscv-64")]
+            "riscv64" => Ok(Self::PVM),
             _ => Err(anyhow::anyhow!(
                 "Unknown target `{}`. Supported targets: {:?}",
                 string,
@@ -50,7 +59,10 @@ impl FromStr for Target {
 impl std::fmt::Display for Target {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         match self {
+            #[cfg(not(feature = "riscv-64"))]
             Target::PVM => write!(f, "riscv32"),
+            #[cfg(feature = "riscv-64")]
+            Target::PVM => write!(f, "riscv64"),
         }
     }
 }