Only use getrandom on recent glibc, when TLS not in use.

lib/util_mosq.c

@@ -28,9 +28,11 @@ Contributors:
 #  include <sys/stat.h>
 #endif
 
-#ifdef __linux__
+#if !defined(WITH_TLS) && defined(__linux__)
+#  if defined(__GLIBC__) && __GLIBC_PREREQ(2, 25)
 #    include <sys/random.h>
 #  endif
+#endif
 
 #ifdef WITH_TLS
 #  include <openssl/bn.h>
@@ -310,8 +312,7 @@ int util__random_bytes(void *bytes, int count)
 	if(RAND_bytes(bytes, count) == 1){
 		rc = MOSQ_ERR_SUCCESS;
 	}
-#else
-#  ifdef __GLIBC__
+#elif defined(__GLIBC__) && __GLIBC_PREREQ(2, 25)
 	if(getrandom(bytes, count, 0) == 0){
 		rc = MOSQ_ERR_SUCCESS;
 	}
@@ -334,7 +335,6 @@ int util__random_bytes(void *bytes, int count)
 		((uint8_t *)bytes)[i] = (uint8_t )(random()&0xFF);
 	}
 	rc = MOSQ_ERR_SUCCESS;
-#  endif
 #endif
 	return rc;
 }