Check for Linux before trying to import sys/random.h

Sources/Cbsspeke/bsspeke.c

@@ -22,7 +22,9 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#if defined(__linux__)
 #include <sys/random.h>
+#endif
 
 /*
 For Emscripten compilation to Javascript use the following: