stop ./configure on Win32 if no library sources was specified,

the bug has been introduced in r2894

auto/lib/openssl/conf

@@ -54,7 +54,10 @@ else
             have=NGX_SSL . auto/have
             CORE_LIBS="$CORE_LIBS $ngx_feature_libs $NGX_LIBDL"
             OPENSSL=YES
-        else
+        fi
+    fi
+
+    if [ $OPENSSL != YES ]; then
 
 cat << END
 
@@ -64,8 +67,7 @@ into the system, or build the OpenSSL library statically from the source
 with nginx by using --with-openssl=<path> option.
 
 END
-            exit 1
-        fi
+        exit 1
     fi
 
 fi