sched.h is only needed for CPU_* interface, only used on glibc. Fixes some mingw versions build

src/core/combined_workers.c

@@ -21,7 +21,9 @@
 #include <common/config.h>
 #include <core/workers.h>
 
+#ifdef __GLIBC__
 #include <sched.h>
+#endif
 
 #ifdef __MINGW32__
 #include <windows.h>