Clean up include path and flag-check

node_api.h must be included from the normal node include path when
we can use the built-in API.

The variable needsFlag must be true from version 8.0.0 inclusive until
version 8.6.0 non-inclusive.

Fixes: #139

Author: Gabriel Schulhof

index.js

@@ -17,22 +17,27 @@ var versionArray = process.version
 var isNodeApiBuiltin =
   (versionArray[0] > 8 || (versionArray[0] == 8 && versionArray[1] > 5));
 
-// So far it looks like even version 9 will need the flag. We need to adjust
-// this for the version where the flag is dropped whenever that version lands.
-var needsFlag = (versionArray[0] >= 8);
+// The flag is not needed when the Node version is not 8, nor if the API is
+// built-in, because we removed the flag at the same time as creating the final
+// incarnation of the built-in API.
+var needsFlag =
+    !(isNodeApiBuiltin || versionArray[0] < 8 || versionArray[0] > 8);
 
-var include = path.join(__dirname, 'src');
+var include = [];
 var gyp = path.join(__dirname, 'src', 'node_api.gyp');
 
 if (isNodeApiBuiltin) {
    gyp += ':nothing';
 } else {
-   gyp += ':node-api';
-   include = path.join(__dirname, 'external-napi');
+  gyp += ':node-api';
+  include = [
+    '"' + path.join(__dirname, 'external-napi') + '"',
+    '"' + __dirname + '"'
+  ];
 }
 
 module.exports = {
-   include: [ '"' + include + '"', '"' + __dirname + '"' ].join(' '),
+   include: include.join(' '),
    gyp: gyp,
    isNodeApiBuiltin: isNodeApiBuiltin,
    needsFlag: needsFlag