cksum: adding -b as the short form for --base64

closes #5706

src/uu/cksum/src/cksum.rs

@@ -448,6 +448,7 @@ pub fn uu_app() -> Command {
         .arg(
             Arg::new(options::BASE64)
             .long(options::BASE64)
+            .short('b')
             .help("emit a base64 digest, not hexadecimal")
             .action(ArgAction::SetTrue)
             // Even though this could easily just override an earlier '--raw',

tests/by-util/test_cksum.rs

@@ -379,14 +379,16 @@ fn test_base64_raw_conflicts() {
 #[test]
 fn test_base64_single_file() {
     for algo in ALGOS {
+        for base64_option in ["--base64", "-b"] {
             new_ucmd!()
-            .arg("--base64")
+                .arg(base64_option)
                 .arg("lorem_ipsum.txt")
                 .arg(format!("--algorithm={algo}"))
                 .succeeds()
                 .no_stderr()
                 .stdout_is_fixture_bytes(format!("base64/{algo}_single_file.expected"));
         }
+    }
 }
 #[test]
 fn test_base64_multiple_files() {