build: allow for overwriting of use_openssl_def

PR-URL: #23763
Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>

node.gyp

@@ -220,9 +220,9 @@
       [ 'OS=="win" and '
         'node_use_openssl=="true" and '
         'node_shared_openssl=="false"', {
-        'use_openssl_def': 1,
+        'use_openssl_def%': 1,
       }, {
-        'use_openssl_def': 0,
+        'use_openssl_def%': 0,
       }],
     ],
   },