Configure: fix build with -Werror=unused-but-set-variable.

Signed-off-by: Piotr Sikora <piotrsikora@google.com>
diff --git a/auto/os/solaris b/auto/os/solaris
index d39df0b..1dcfe84 100644
--- a/auto/os/solaris
+++ b/auto/os/solaris
@@ -52,7 +52,7 @@
 ngx_feature_incs="#include <port.h>"
 ngx_feature_path=
 ngx_feature_libs=
-ngx_feature_test="int n = port_create()"
+ngx_feature_test="(void) port_create()"
 . auto/feature
 
 if [ $ngx_found = yes ]; then