Rollup merge of #83231 - DieracDelta:lp64d-abi-for-riscvgc-unknown-none-elf, r=estebank

Switch riscvgc-unknown-none-elf use lp64d ABI

Corrects #83229 by directly specifying the target abi in the spec in the same way as is done for the `riscv64gc-unknown-linux-gnu` target [here](https://github.com/rust-lang/rust/blob/master/compiler/rustc_target/src/spec/riscv64gc_unknown_linux_gnu.rs).

Author: Dylan-DPC

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,