build: update build targets for io.js

PR-URL: https://github.com/nodejs/io.js/pull/1938
Reviewed-By: Johan Bergström <[email protected]>
Reviewed-By: Ben Noordhuis <[email protected]>
Reviewed-By: Alexis Campailla <[email protected]>
diff --git a/node.gyp b/node.gyp
index 2b530f1..dfa08ce 100644
--- a/node.gyp
+++ b/node.gyp
@@ -184,12 +184,15 @@
       'defines': [
         'NODE_ARCH="<(target_arch)"',
         'NODE_PLATFORM="<(OS)"',
-        'NODE_TAG="<(node_tag)"',
         'NODE_V8_OPTIONS="<(node_v8_options)"',
         'NODE_WANT_INTERNALS=1',
       ],
 
+
       'conditions': [
+        [ 'node_tag!=""', {
+          'defines': [ 'NODE_TAG="<(node_tag)"' ],
+        }],
         # No node_main.cc for anything except executable
         [ 'node_target_type!="executable"', {
           'sources!': [