Enable cranelift on linux for compiling rust faster.

This is based on https://bjorn3.github.io/2023/10/31/progress-report-oct-2023.html.

ansible/roles/rust/files/cargo_config.toml

@@ -1,2 +1,12 @@
 [target.x86_64-unknown-linux-gnu]
 rustflags = ["-C", "target-cpu=native", "-Zthreads=0"]
+
+[unstable]
+codegen-backend = true
+
+[profile.dev]
+codegen-backend = "cranelift"
+
+[profile.dev.package."*"]
+codegen-backend = "llvm"
+opt-level = 3