riscvgc-unknown-none-elf use lp64d ABI

Author: Justin Restivo

compiler/rustc_target/src/spec/riscv64gc_unknown_none_elf.rs

@@ -11,6 +11,7 @@ pub fn target() -> Target {
         options: TargetOptions {
             linker_flavor: LinkerFlavor::Lld(LldFlavor::Ld),
             linker: Some("rust-lld".to_string()),
+            llvm_abiname: "lp64d".to_string(),
             cpu: "generic-rv64".to_string(),
             max_atomic_width: Some(64),
             atomic_cas: true,