build(uci): restrict UCI dependency and feature to Linux targets

Ensure the UCI integration is only compiled on Linux, as the underlying native dependency is platform-specific. Added a build script to warn users when the feature is enabled on unsupported platforms.

Cargo.toml

@@ -25,7 +25,6 @@ netlink-bindings = { git = "https://github.com/one-d-wide/netlink-bindings.git",
 netlink-socket2 = { git = "https://github.com/one-d-wide/netlink-bindings.git", rev = "0b609e9380610e7da73f8c43cdf804a1d1bf5474" }
 fastrand = "2"
 rustix = { version = "1.1", features = ["fs", "system", "thread", "time"] }
-rust-uci = { git = "https://github.com/namib-project/rust-uci.git", rev = "3e7b6153b6df92b45428c32bb6461756563deecb", optional = true }
 thiserror = "2.0"
 libc = "0.2"
 flume = { version = "0.12.0",  default-features = false, features = ["eventual-fairness", "select"] }
@@ -34,5 +33,8 @@ flume = { version = "0.12.0",  default-features = false, features = ["eventual-f
 features = ["std"]
 version = "0.4"
 
+[target.'cfg(target_os = "linux")'.dependencies]
+rust-uci = { git = "https://github.com/namib-project/rust-uci.git", rev = "3e7b6153b6df92b45428c32bb6461756563deecb", optional = true }
+
 [features]
 uci = ["dep:rust-uci"]