build: musl static binary + native + strip

.cargo/config.toml

@@ -0,0 +1,3 @@
+[build]
+target = "x86_64-unknown-linux-musl"
+rustflags = "-C target-cpu=native -C strip=symbols"

src/main.rs

@@ -1,3 +1,5 @@
+use std::time::Instant;
+
 struct SField {
     field: Vec<usize>,
     fixed: Vec<usize>,
@@ -401,9 +403,11 @@ impl SField {
 
     #[inline(always)]
     fn solve(&mut self) {
+        let now = Instant::now();
         if !self.solve_backtracking() {
             println!("there is no solution.");
         }
+        println!("took {:.3}s", now.elapsed().as_secs_f64());
     }
 }