configure: create and use a 'config.gypi' file

This is like how node does it with its ./configure script.

Closes #32.

lib/configure.js

@@ -9,6 +9,7 @@ var fs = require('fs')
   , path = require('path')
   , glob = require('glob')
   , semver = require('semver')
+  , mkdirp = require('./util/mkdirp')
   , createHook = require('./util/hook')
   , asyncEmit = require('./util/asyncEmit')
   , win = process.platform == 'win32'
@@ -18,6 +19,8 @@ exports.usage = 'Generates ' + (win ? 'MSVC project files' : 'a Makefile') + ' f
 function configure (gyp, argv, callback) {
 
   var python = gyp.opts.python || 'python'
+    , buildDir = path.resolve('build')
+    , configPath
     , emitter
     , versionStr
     , version
@@ -46,10 +49,45 @@ function configure (gyp, argv, callback) {
     }
     version = version.slice(1, 4).join('.')
     gyp.opts.ensure = true
-    gyp.commands.install([ version ], go)
+    gyp.commands.install([ version ], createBuildDir)
   }
 
-  function go (err) {
+  function createBuildDir (err) {
+    if (err) return callback(err)
+    gyp.verbose('attempting to create "build" dir', buildDir)
+    mkdirp(buildDir, function (err, isNew) {
+      if (err) return callback(err)
+      gyp.verbose('"build" dir needed to be created?', isNew)
+      createConfigFile()
+    })
+  }
+
+  function createConfigFile (err) {
+    if (err) return callback(err)
+    gyp.verbose('creating build/config.gypi file')
+
+    var config = {}
+    configPath = path.resolve(buildDir, 'config.gypi')
+
+    config.target_defaults = {
+        cflags: []
+      , default_configuration: gyp.opts.debug ? 'Debug' : 'Release'
+      , defines: []
+      , include_dirs: []
+      , libraries: []
+    }
+
+    config.variables = {
+        target_arch: gyp.opts.arch || process.arch || 'ia32'
+    }
+
+    var prefix = '# Do not edit. File was generated by node-gyp\'s "configure" step'
+      , json = JSON.stringify(config, null, 2)
+    gyp.verbose('writing out config file', configPath)
+    fs.writeFile(configPath, [prefix, json, ''].join('\n'), runGypAddon)
+  }
+
+  function runGypAddon (err) {
     if (err) return callback(err)
 
     var devDir = path.resolve(process.env.HOME, '.node-gyp', version)
@@ -61,25 +99,8 @@ function configure (gyp, argv, callback) {
       argv.push('-f', 'make')
     }
 
-    var hasArch = argv.some(function (arg) {
-      return arg.indexOf('-Dtarget_arch') === 0
-    })
-    // was --arch specified?
-    if (!hasArch && gyp.opts.arch) {
-      gyp.verbose('using the architecture specified by --arch', gyp.opts.arch)
-      argv.push('-Dtarget_arch=' + gyp.opts.arch)
-      hasArch = true
-    }
-
-    // this may need to be tweaked for windows and stuff, we'll see...
-    if (!hasArch) {
-      // on < 0.8 the target_arch variable is set to ia32 by default unless
-      // overridden, so we have to explicitly specify the arch here
-      gyp.verbose('target arch not specified, using the current host architecture', process.arch)
-      argv.push('-Dtarget_arch=' + process.arch)
-      gyp.opts.arch = process.arch
-      hasArch = true
-    }
+    // include the "config.gypi" file that was generated
+    argv.unshift('-I' + configPath)
 
     // enforce use of the "binding.gyp" file
     argv.unshift('binding.gyp')