fix spawn EINVAL error

fixes prebuild#83

index.js

@@ -1,5 +1,4 @@
-var proc = require('child_process')
-var execspawn = require('execspawn')
+var childProcess = require('child_process')
 var os = require('os')
 var path = require('path')
 var fs = require('fs')
@@ -19,7 +18,7 @@ function prebuildify (opts, cb) {
  strip: process.env.PREBUILD_STRIP === '1',
  stripBin: process.env.PREBUILD_STRIP_BIN || 'strip',
  nodeGyp: process.env.PREBUILD_NODE_GYP || npmbin('node-gyp'),
- shell: process.env.PREBUILD_SHELL || shell(),
+ shell: process.env.PREBUILD_SHELL || true,
  cwd: '.',
  targets: []
  }, opts)
@@ -179,11 +178,12 @@ function copySharedLibs (builds, folder, opts, cb) {
 function run (cmd, opts, cb) {
  if (!cmd) return cb()
 
- var child = execspawn(cmd, {
+ var child = childProcess.spawn(cmd, [], {
  cwd: opts.cwd,
  env: opts.env,
- stdio: 'inherit',
- shell: opts.shell
+ stdio: opts.quiet ? 'ignore' : 'inherit',
+ shell: opts.shell,
+ windowsHide: true
  })
 
  child.on('exit', function (code) {
@@ -227,9 +227,11 @@ function build (target, runtime, opts, cb) {
  }
 
  mkdirp(cache, function () {
- var child = proc.spawn(opts.nodeGyp, args, {
+ var child = childProcess.spawn(opts.nodeGyp, args, {
  cwd: opts.cwd,
  env: opts.env,
+ shell: opts.shell,
+ windowsHide: true,
  stdio: opts.quiet ? 'ignore' : 'inherit'
  })
 
@@ -266,7 +268,13 @@ function strip (file, opts, cb) {
  if (!opts.strip || (platform !== 'darwin' && platform !== 'linux')) return cb()
 
  var args = platform === 'darwin' ? [file, '-Sx'] : [file, '--strip-all']
- var child = proc.spawn(opts.stripBin, args, { stdio: 'ignore' })
+ var child = childProcess.spawn(opts.stripBin, args, {
+ stdio: 'ignore',
+ cwd: opts.cwd,
+ env: opts.env,
+ shell: opts.shell,
+ windowsHide: true
+ })
 
  child.on('exit', function (code) {
  if (code) return cb(spawnError(opts.stripBin, code))
@@ -299,10 +307,6 @@ function npmbin (name) {
  return os.platform() === 'win32' ? name + '.cmd' : name
 }
 
-function shell () {
- return os.platform() === 'android' ? 'sh' : undefined
-}
-
 function resolveTargets (targets, all, napi, electronCompat) {
  targets = targets.map(function (v) {
  if (typeof v === 'object' && v !== null) return v