clippy: allow "cygwin" as value for "target_os"

Cargo.toml

@@ -619,9 +619,12 @@ workspace = true
 # This is the linting configuration for all crates.
 # In order to use these, all crates have `[lints] workspace = true` section.
 [workspace.lints.rust]
-# Allow "fuzzing" as a "cfg" condition name
+# Allow "fuzzing" as a "cfg" condition name and "cygwin" as a value for "target_os"
 # https://doc.rust-lang.org/nightly/rustc/check-cfg/cargo-specifics.html
-unexpected_cfgs = { level = "warn", check-cfg = ['cfg(fuzzing)'] }
+unexpected_cfgs = { level = "warn", check-cfg = [
+  'cfg(fuzzing)',
+  'cfg(target_os, values("cygwin"))',
+] }
 #unused_qualifications = "warn" // TODO: fix warnings in uucore, then re-enable this lint
 
 [workspace.lints.clippy]

src/uu/stdbuf/src/libstdbuf/Cargo.toml

@@ -10,6 +10,9 @@ keywords.workspace = true
 categories.workspace = true
 edition.workspace = true
 
+[lints]
+workspace = true
+
 [lib]
 name = "stdbuf"
 path = "src/libstdbuf.rs"