Only regenerate magic bitboards when necessary

Author: iCodeSometime

CHANGELOG.md

@@ -1,5 +1,6 @@
 v0.0.3
  - Added optional `tracing` instrumentation to Game - use the `instrument_game` feature to enable.
+ - Additional 3x increase in build speed, by only rebuilding magic bitboards when necessary.
 
 v0.0.2
  - Added `Board::en_passant_target` to match standard meaning - for now, `Board::en_passant` should still be preferred in the hot path.

src/build.rs

@@ -18,5 +18,7 @@ mod square;
 use crate::gen_tables::generate_all_tables;
 // Generate everything.
 fn main() {
+    println!("cargo:rerun-if-changed=src/gen_tables/");
+
     generate_all_tables();
 }