Merge branch 'fix-dummy-build-sleepduration' into 'next'

Fix dummy build

See merge request STJr/SRB2!2242

src/dummy/i_system.c

 #include "../doomdef.h"
 #include "../doomtype.h"
 #include "../i_system.h"
+#include "../i_time.h"
 
 FILE *logstream = NULL;
 
@@ -19,6 +20,11 @@ void I_Sleep(UINT32 ms)
 	(void)ms;
 }
 
+void I_SleepDuration(precise_t duration)
+{
+	(void)duration;
+}
+
 precise_t I_GetPreciseTime(void)
 {
 	return 0;