Fix breakage with latest nightly.

Ref: rust-lang/rust#131807

Author: Arnavion

freestanding/riscv64-arnavion-none-elf.json

@@ -10,6 +10,7 @@
 	"features": "+forced-atomics,+zba,+zbb,+zbs,+zca,+zcb,+zicond,+zicsr,+zicntr,+auipc-addi-fusion,+ld-add-fusion,+lui-addi-fusion",
 	"linker": "rust-lld",
 	"linker-flavor": "gnu-lld",
+	"llvm-abiname": "lp64",
 	"llvm-target": "riscv64",
 	"max-atomic-width": 64,
 	"metadata": {