Update configure.js

Fixes nodejs#65. Build failure when builddir contains spaces.
Solution by @trentm.
See trentm@bbd979b

lib/configure.js

@@ -1,4 +1,3 @@
-
 module.exports = exports = configure
 
 /**
@@ -175,7 +174,7 @@ function configure (gyp, argv, callback) {
 
     var config = process.config || {}
       , defaults = config.target_defaults
-      , variables = config.variables
+      , variablesa = config.variables
 
     // default "config.variables"
     if (!variables) variables = config.variables = {}
@@ -303,13 +302,18 @@ function configure (gyp, argv, callback) {
       // Windows expects an absolute path
       output_dir = buildDir
     }
-
-    argv.push('-I', addon_gypi)
-    argv.push('-I', common_gypi)
+
+    // Fix for spaces and other special characters in path.
+    function shellEscape(str) {
+      return str.replace(/(["\s'$`\\])/g, '\\$1');
+    };
+
+    argv.push('-I', shellEscape(addon_gypi))
+    argv.push('-I', shellEscape(common_gypi))
     argv.push('-Dlibrary=shared_library')
     argv.push('-Dvisibility=default')
-    argv.push('-Dnode_root_dir=' + nodeDir)
-    argv.push('-Dmodule_root_dir=' + process.cwd())
+    argv.push('-Dnode_root_dir=' + shellEscape(nodeDir))
+    argv.push('-Dmodule_root_dir=' + shellEscape(process.cwd()))
     argv.push('--depth=.')
 
     // tell gyp to write the Makefile/Solution files into output_dir