Added getentropy() support.

Prodded by David Carlier.

auto/unix

@@ -48,6 +48,49 @@ if [ $nxt_found = no ]; then
 fi
 
 
+if [ $nxt_found = no ]; then
+
+    # OpenBSD 5.6 lacks <sys/random.h>.
+
+    nxt_feature="getentropy()"
+    nxt_feature_name=NXT_HAVE_GETENTROPY
+    nxt_feature_test="#include <unistd.h>
+
+                      int main() {
+                          char  buf[4];
+
+                          if (getentropy(buf, 4) == -1) {
+                              return 1;
+                          }
+
+                          return 0;
+                      }"
+    . auto/feature
+fi
+
+
+if [ $nxt_found = no ]; then
+
+    # macOS 10.12.
+
+    nxt_feature="getentropy() in sys/random.h"
+    nxt_feature_name=NXT_HAVE_GETENTROPY_SYS_RANDOM
+    nxt_feature_test="#include <unistd.h>
+                      #include <sys/random.h>
+
+                      int main() {
+                          char  buf[4];
+
+                          if (getentropy(buf, 4) == -1) {
+                              return 1;
+                          }
+
+                          return 0;
+                      }"
+    . auto/feature
+fi
+
+
 nxt_feature="ucontext"
 nxt_feature_name=NXT_HAVE_UCONTEXT
 nxt_feature_run=

src/nxt_random.c

@@ -68,6 +68,14 @@ nxt_random_stir(nxt_random_t *r)
 
     n = syscall(SYS_getrandom, &key, NXT_RANDOM_KEY_SIZE, 0);
 
+#elif (NXT_HAVE_GETENTROPY || NXT_HAVE_GETENTROPY_SYS_RANDOM)
+
+    n = 0;
+
+    if (getentropy(&key, NXT_RANDOM_KEY_SIZE) == 0) {
+        n = NXT_RANDOM_KEY_SIZE;
+    }
+
 #else
 
     n = 0;

src/nxt_unix.h

@@ -234,6 +234,8 @@
 #include <sys/random.h>             /* getrandom(). */
 #elif (NXT_HAVE_LINUX_SYS_GETRANDOM)
 #include <linux/random.h>           /* SYS_getrandom. */
+#elif (NXT_HAVE_GETENTROPY_SYS_RANDOM)
+#include <sys/random.h>             /* getentropy(). */
 #endif