Fix compilation problem related to getrandom() on non-glibc systems.

ChangeLog.txt

@@ -9,6 +9,7 @@ Broker:
   with glibc >= 2.25. Without this fix, no random numbers would be generated
   for e.g. on broker client id generation, and so clients connecting expecting
   this feature would be unable to connect.
+- Fix compilation problem related to getrandom() on non-glibc systems.
 
 Clients:
 - Fix -L url parsing when `/topic` part is missing.

lib/util_mosq.c

@@ -28,9 +28,10 @@ Contributors:
 #  include <sys/stat.h>
 #endif
 
-#if !defined(WITH_TLS) && defined(__linux__)
-#  if defined(__GLIBC__) && __GLIBC_PREREQ(2, 25)
+#if !defined(WITH_TLS) && defined(__linux__) && defined(__GLIBC__)
+#  if __GLIBC_PREREQ(2, 25)
 #    include <sys/random.h>
+#    define HAVE_GETRANDOM 1
 #  endif
 #endif
 
@@ -325,7 +326,7 @@ int util__random_bytes(void *bytes, int count)
 	if(RAND_bytes(bytes, count) == 1){
 		rc = MOSQ_ERR_SUCCESS;
 	}
-#elif defined(__GLIBC__) && __GLIBC_PREREQ(2, 25)
+#elif defined(HAVE_GETRANDOM)
 	if(getrandom(bytes, count, 0) == count){
 		rc = MOSQ_ERR_SUCCESS;
 	}