fix lib path resolving in scripts/paths.js (microsoft#56)

* fix lib path resolving in scripts/paths.js

* throw error when it fails to resolve the lib path by require('napajs/build').paths

scripts/paths.js

@@ -3,9 +3,18 @@
 
 let path = require('path');
 
+Object.defineProperty(exports, 'root', {
+    get: function() {
+        let rootPath = path.resolve(__dirname, '..');
+        // Output the path to stdout for cmake/gyp commands.
+        process.stdout.write(rootPath);
+        return rootPath;
+    }
+});
+
 Object.defineProperty(exports, 'lib', {
     get: function() {
-        let libPath = path.resolve(__dirname, '../inc/' + getLibraryName('napa'));
+        let libPath = path.resolve(__dirname, '../bin/' + getLibraryName('napa'));
         // Output the path to stdout for cmake/gyp commands.
         process.stdout.write(libPath);
         return libPath;
@@ -29,6 +38,10 @@ function getLibraryName(originalName) {
         return 'lib' + originalName + '.dylib';
     } else if (process.platform === 'linux') {
         return 'lib' + originalName + '.so';
+    } else {
+        throw new Error(
+            'Failed to resolve the library name of "' + originalName +
+            '" because your platform type "' + process.platform +
+            '"is not supported by require(\'napajs/build\').paths');
     }
-    return originalName;
 }