Tail macos stdin ran from script fix (#7844)

* fixes #7763

- introduce macOS-specific config guard
- added test for testing tail stdin when redirected (`>`) from file and
  when through a pipe (`|`)

* created test to mock behavior in #7763, with comments

added drop line

* re-enabled test_stdin_redirect_dir_when_target_os_is_macos, and added a check to handle error message

* added location of current directory so test env can find script

* adjusting to try to have FreeBSD find the file in CI test

* putting in /env instead of assuming bash

* removed ignore macro

* added comments explaining the need for specific macOS cases, including reference to rust-lang issue: https://github.com/rust-lang/rust/issues/95239

tests/by-util/test_tail.rs

@@ -346,6 +346,55 @@ fn test_stdin_redirect_dir_when_target_os_is_macos() {
         .stderr_is("tail: cannot open 'standard input' for reading: No such file or directory\n");
 }
 
+#[test]
+#[cfg(unix)]
+fn test_stdin_via_script_redirection_and_pipe() {
+    // $ touch file.txt
+    // $ echo line1 > file.txt
+    // $ echo line2 >> file.txt
+    // $ chmod +x test.sh
+    // $ ./test.sh < file.txt
+    // line1
+    // line2
+    // $ cat file.txt | ./test.sh
+    // line1
+    // line2
+    use std::os::unix::fs::PermissionsExt;
+
+    let scene = TestScenario::new(util_name!());
+    let at = &scene.fixtures;
+    let data = "line1\nline2\n";
+
+    at.write("file.txt", data);
+
+    let mut script = at.make_file("test.sh");
+    writeln!(script, "#!/usr/bin/env sh").unwrap();
+    writeln!(script, "tail").unwrap();
+    script
+        .set_permissions(PermissionsExt::from_mode(0o755))
+        .unwrap();
+
+    drop(script); // close the file handle to ensure file is not busy
+
+    // test with redirection
+    scene
+        .cmd("sh")
+        .current_dir(at.plus(""))
+        .arg("-c")
+        .arg("./test.sh < file.txt")
+        .succeeds()
+        .stdout_only(data);
+
+    // test with pipe
+    scene
+        .cmd("sh")
+        .current_dir(at.plus(""))
+        .arg("-c")
+        .arg("cat file.txt | ./test.sh")
+        .succeeds()
+        .stdout_only(data);
+}
+
 #[test]
 fn test_follow_stdin_descriptor() {
     let ts = TestScenario::new(util_name!());