https://github.com/cutechess/cutechess/pull/831
https://bugs.gentoo.org/944259

--- a/projects/lib/3rdparty/fathom/src/tbconfig.h
+++ b/projects/lib/3rdparty/fathom/src/tbconfig.h
@@ -66,7 +66,6 @@
  * Define TB_NO_STDBOOL if you do not want to use <stdbool.h> or it is not
  * available or unnecessary (e.g. C++).
  */
-#define TB_NO_STDBOOL
 
 /*
  * Define TB_NO_THREADS if your program is not multi-threaded.