Guard "sys/random.h" with HAVE_GETENTROPY

[olegrok]

After 59b2f66 compilation on e.g. centos:7 started to fail on "sys/random.h".

Fix is quite straightforward:

diff --git a/src/rdrand.c b/src/rdrand.c
index 77d02cfc..ad388e2a 100644
--- a/src/rdrand.c
+++ b/src/rdrand.c
@@ -32,10 +32,12 @@
 #include "tinycthread.h"
 #include "rdmurmur2.h"
 #ifndef _WIN32
+#ifdef HAVE_GETENTROPY
 /* getentropy() can be present in one of these two */
 #include <unistd.h>
 #include <sys/random.h>
 #endif
+#endif
 
 #ifdef HAVE_OSSL_SECURE_RAND_BYTES
 #include <openssl/rand.h>

[ThomasDevoogdt]

I found the the same issue independently, here is my PR: #5310

[alopezz]

Same here: #5298.