fix(redox): gate Metadata and nix-dependent methods for Redox compatibility

Fixes compilation errors on Redox by properly gating code that depends on
nix crate types (FileStat) which are not available on Redox.

Changes:
- Add direct libc import for Redox (nix::libc not available)
- Gate Metadata struct, impl, and MetadataExt trait (use FileStat)
- Gate metadata_at() and metadata() methods (return Metadata)
- Revert unrelated locale test changes from commit 5704355

The Redox platform lacks support for nix::sys::stat::FileStat, causing
build failures. These items now follow the existing pattern of returning
"safe_traversal is not supported on Redox" errors via gated stub methods.

Author: abendrothj

src/uu/date/src/locale.rs

@@ -121,62 +121,39 @@ mod tests {
         #[test]
         fn test_default_format_contains_valid_codes() {
             let format = get_locale_default_format();
-            // On platforms without locale support, fallback may not contain all codes
-            #[cfg(any(
-                target_os = "linux",
-                target_vendor = "apple",
-                target_os = "freebsd",
-                target_os = "netbsd",
-                target_os = "openbsd",
-                target_os = "dragonfly"
-            ))]
-            {
-                // We only strictly check for timezone because ensure_timezone_in_format guarantees it
-                assert!(format.contains("%Z") || format.contains("%z")); // timezone
-
-                // Other components depend on the system locale and might vary (e.g. %F, %c, etc.)
-                // so we don't strictly assert %a or %b here.
-            }
+            assert!(format.contains("%a")); // abbreviated weekday
+            assert!(format.contains("%b")); // abbreviated month
+            assert!(format.contains("%Y") || format.contains("%y")); // year (4-digit or 2-digit)
+            assert!(format.contains("%Z")); // timezone
         }
 
         #[test]
         fn test_locale_format_structure() {
+            // Verify we're using actual locale format strings, not hardcoded ones
             let format = get_locale_default_format();
+
+            // The format should not be empty
             assert!(!format.is_empty(), "Locale format should not be empty");
-            #[cfg(any(
-                target_os = "linux",
-                target_vendor = "apple",
-                target_os = "freebsd",
-                target_os = "netbsd",
-                target_os = "openbsd",
-                target_os = "dragonfly"
-            ))]
-            {
-                let has_date_component = format.contains("%a")
-                    || format.contains("%A")
-                    || format.contains("%b")
-                    || format.contains("%B")
-                    || format.contains("%d")
-                    || format.contains("%e")
-                    || format.contains("%F") // YYYY-MM-DD
-                    || format.contains("%D") // MM/DD/YY
-                    || format.contains("%x") // Locale's date representation
-                    || format.contains("%c") // Locale's date and time
-                    || format.contains("%+"); // date(1) extended format
-                assert!(has_date_component, "Format should contain date components");
-
-                let has_time_component = format.contains("%H")
-                    || format.contains("%I")
-                    || format.contains("%k")
-                    || format.contains("%l")
-                    || format.contains("%r")
-                    || format.contains("%R")
-                    || format.contains("%T")
-                    || format.contains("%X")
-                    || format.contains("%c") // Locale's date and time
-                    || format.contains("%+"); // date(1) extended format
-                assert!(has_time_component, "Format should contain time components");
-            }
+
+            // Should contain date/time components
+            let has_date_component = format.contains("%a")
+                || format.contains("%A")
+                || format.contains("%b")
+                || format.contains("%B")
+                || format.contains("%d")
+                || format.contains("%e");
+            assert!(has_date_component, "Format should contain date components");
+
+            // Should contain time component (hour)
+            let has_time_component = format.contains("%H")
+                || format.contains("%I")
+                || format.contains("%k")
+                || format.contains("%l")
+                || format.contains("%r")
+                || format.contains("%R")
+                || format.contains("%T")
+                || format.contains("%X");
+            assert!(has_time_component, "Format should contain time components");
         }
 
         #[test]

src/uucore/src/lib/features/safe_traversal.rs

@@ -30,6 +30,8 @@ use nix::libc;
 use nix::sys::stat::{FchmodatFlags, FileStat, Mode, fchmodat, fstatat};
 #[cfg(not(target_os = "redox"))]
 use nix::unistd::{Gid, Uid, UnlinkatFlags, fchown, fchownat, unlinkat};
+#[cfg(target_os = "redox")]
+use libc;
 use os_display::Quotable;
 
 use crate::translate;
@@ -249,11 +251,13 @@ impl DirFd {
     }
 
     /// Get metadata for a file relative to this directory
+    #[cfg(not(target_os = "redox"))]
     pub fn metadata_at(&self, name: &OsStr, follow_symlinks: bool) -> io::Result<Metadata> {
         self.stat_at(name, follow_symlinks).map(Metadata::from_stat)
     }
 
     /// Get metadata for this directory
+    #[cfg(not(target_os = "redox"))]
     pub fn metadata(&self) -> io::Result<Metadata> {
         self.fstat().map(Metadata::from_stat)
     }
@@ -470,11 +474,13 @@ impl FileType {
 }
 
 /// Metadata wrapper for safer access to file information
+#[cfg(not(target_os = "redox"))]
 #[derive(Debug, Clone)]
 pub struct Metadata {
     stat: FileStat,
 }
 
+#[cfg(not(target_os = "redox"))]
 impl Metadata {
     pub fn from_stat(stat: FileStat) -> Self {
         Self { stat }
@@ -523,6 +529,7 @@ impl Metadata {
 }
 
 // Add MetadataExt trait implementation for compatibility
+#[cfg(not(target_os = "redox"))]
 impl std::os::unix::fs::MetadataExt for Metadata {
     // st_dev type varies by platform (i32 on macOS, u64 on Linux)
     #[allow(clippy::unnecessary_cast)]