BUILD: SSL: add BoringSSL guarding to "RAND_keep_random_devices_open"

"RAND_keep_random_devices_open" is OpenSSL specific, does not present
in other OpenSSL variants like LibreSSL or BoringSSL. BoringSSL recently
"updated" its internal openssl version to 1.1.1, we temporarily set it
back to 1.1.0, as we are going to remove that hack, let us add proper
guarding.
diff --git a/src/haproxy.c b/src/haproxy.c
index 019cc57..ae11f8d 100644
--- a/src/haproxy.c
+++ b/src/haproxy.c
@@ -783,7 +783,7 @@
 		if (fdtab)
 			deinit_pollers();
 	}
-#if defined(USE_OPENSSL) && (HA_OPENSSL_VERSION_NUMBER >= 0x10101000L)
+#if defined(USE_OPENSSL) && (HA_OPENSSL_VERSION_NUMBER >= 0x10101000L) && !defined(OPENSSL_IS_BORINGSSL)
 	/* close random device FDs */
 	RAND_keep_random_devices_open(0);
 #endif