df: fix unused imports/variables on non-Unix platforms

Author: ChrisDryden

src/uu/df/src/df.rs

@@ -367,7 +367,7 @@ where
     // The list of all mounted filesystems.
     let mounts_result = read_fs_list();
 
-    let (mounts, use_fallback) = match mounts_result {
+    let (mounts, _use_fallback) = match mounts_result {
         Ok(m) => (m, false),
         Err(e) => {
             if opt.requires_mount_table() {
@@ -387,7 +387,7 @@ where
     // both the mount information and usage information.
     for path in paths {
         #[cfg(unix)]
-        let fs_result = if use_fallback {
+        let fs_result = if _use_fallback {
             Filesystem::from_path_direct(path)
         } else {
             Filesystem::from_path(&mounts, path)

src/uu/df/src/filesystem.rs

@@ -8,7 +8,9 @@
 //! filesystem mounted at a particular directory. It also includes
 //! information on amount of space available and amount of space used.
 // spell-checker:ignore canonicalized
+#[cfg(unix)]
 use std::io;
+#[cfg(unix)]
 use std::path::PathBuf;
 use std::{ffi::OsString, path::Path};
 

tests/by-util/test_df.rs

@@ -15,6 +15,7 @@ use std::collections::HashSet;
 #[cfg(not(any(target_os = "freebsd", target_os = "windows")))]
 use uutests::at_and_ucmd;
 use uutests::new_ucmd;
+#[cfg(target_os = "linux")]
 use uutests::util::TestScenario;
 
 #[test]