fix: compilation error on x86 soft float targets

The breaking change of nightly rust 2025-02-04 caused
x86 soft float targets refusing to compile.

Fix it according to the solution provided in
`https://github.com/rust-lang/rust/issues/136544`

x86_64-unknown-none.json

@@ -11,5 +11,6 @@
     "linker": "rust-lld",
     "panic-strategy": "abort",
     "disable-redzone": true,
-    "features": "-mmx,-sse,+soft-float"
+    "features": "-mmx,-sse,+soft-float",
+    "rustc-abi": "x86-softfloat"
 }