Build Linux-only functions only on Linux

components/entropy.c

@@ -1,4 +1,5 @@
 /* See LICENSE file for copyright and license details. */
+#ifdef __linux__
 #include <stdio.h>
 
 #include "../util.h"
@@ -11,3 +12,4 @@ entropy(void)
 	return (pscanf("/proc/sys/kernel/random/entropy_avail", "%d", &num) == 1) ?
 	               bprintf("%d", num) : NULL;
 }
+#endif