Fix issue #118

Check for _tvOS_ or _watchOS_ to call `getentropy` (instead of using `syscall`)

src/chacha20poly1305.c

@@ -370,13 +370,20 @@ static size_t read_urandom(void* buf, size_t n)
   return 0;
 }
 
+#if defined(__APPLE__)
+#include "TargetConditionals.h"
+#endif
+
 #if defined(__APPLE__) && defined(__MAC_10_12) && !defined(__IPHONE_OS_VERSION_MIN_REQUIRED)
 #include <sys/random.h>
 #endif
 
 static size_t entropy(void* buf, size_t n)
 {
-#if defined(__APPLE__) && defined(__MAC_10_12) && __MAC_OS_X_VERSION_MAX_ALLOWED >= __MAC_10_12
+#if defined(__APPLE__) && ((defined(__MAC_10_12) && __MAC_OS_X_VERSION_MAX_ALLOWED >= __MAC_10_12) || TARGET_OS_TV || TARGET_OS_WATCH)
+#if TARGET_OS_TV || TARGET_OS_WATCH
+  extern int getentropy(void* buffer, size_t buflen);
+#endif
   if (getentropy(buf, n) == 0)
     return n;
 #elif defined(__linux__) && defined(SYS_getrandom)