printf: Ignore thousand seperator flag

Author: sargas

src/uucore/src/lib/features/format/spec.rs

@@ -108,6 +108,10 @@ impl Flags {
                 b' ' => flags.space = true,
                 b'#' => flags.hash = true,
                 b'0' => flags.zero = true,
+                b'\'' => {
+                    // the thousands separator is printed with numbers using the ' flag, but
+                    // this is a no-op in the "C" locale.
+                }
                 _ => break,
             }
             *index += 1;