rust: support Rust >= 1.91.0 target spec

Starting with Rust 1.91.0 (expected 2025-10-30), the target spec format
has changed the type of the `target-pointer-width` key from string
to integer.

Thus conditionally use one or the other depending on the version.

Link: rust-lang/rust#144443 [1]
Signed-off-by: Miguel Ojeda <[email protected]>

Author: ojeda

scripts/generate_rust_target.rs

@@ -225,7 +225,11 @@ fn main() {
         ts.push("features", features);
         ts.push("llvm-target", "x86_64-linux-gnu");
         ts.push("supported-sanitizers", ["kcfi", "kernel-address"]);
-        ts.push("target-pointer-width", "64");
+        if cfg.rustc_version_atleast(1, 91, 0) {
+            ts.push("target-pointer-width", 64);
+        } else {
+            ts.push("target-pointer-width", "64");
+        }
     } else if cfg.has("X86_32") {
         // This only works on UML, as i386 otherwise needs regparm support in rustc
         if !cfg.has("UML") {
@@ -245,7 +249,11 @@ fn main() {
         }
         ts.push("features", features);
         ts.push("llvm-target", "i386-unknown-linux-gnu");
-        ts.push("target-pointer-width", "32");
+        if cfg.rustc_version_atleast(1, 91, 0) {
+            ts.push("target-pointer-width", 32);
+        } else {
+            ts.push("target-pointer-width", "32");
+        }
     } else if cfg.has("LOONGARCH") {
         panic!("loongarch uses the builtin rustc loongarch64-unknown-none-softfloat target");
     } else {