Improve emscripten download, install and auto-detection

build_tools/download_emscripten.py

 #!/usr/bin/env python
 # Copyright 2015 The Native Client Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 """Download the Emscripten SDK for the current platform.
 
 This script downloads the emscripten tarball and expands it.
 It requires gsutil to be in the bin PATH and is currently
 supported on Linux and Mac OSX and not windows.
-
-Additional prerequisites include cmake, node.js and Java.
 """
 
 import os
 import subprocess
 import sys
 import tarfile
 
 SCRIPT_DIR = os.path.dirname(os.path.abspath(__file__))
 NACLPORTS_ROOT = os.path.dirname(SCRIPT_DIR)
 sys.path.append(os.path.join(NACLPORTS_ROOT, 'lib'))
@@ skipping 27 matching lines @@
       naclports.Log("Verified cached file: %s" % filename)
       return full_name
     except naclports.util.HashVerificationError:
       naclports.Log("Hash mistmatch on cached download: %s" % filename)
 
   naclports.DownloadFile(full_name, url)
   naclports.util.VerifyHash(full_name, sha1)
   return full_name
 
 
-def DownloadAndExtract(url, sha1, target_dir):
+def DownloadAndExtract(url, sha1, target_dir, link_name=None):
   tar_file = DownloadToCache(url, sha1)
 
   if not os.path.exists(OUT_DIR):
     os.makedirs(OUT_DIR)
 
   os.chdir(OUT_DIR)
 
   # Remove previously extracted archive
   if os.path.exists(target_dir):
     naclports.Log('Cleaning up existing %s...' % target_dir)
     cmd = ['rm', '-rf']
     cmd.append(target_dir)
     subprocess.check_call(cmd)
 
   # Extract archive
   naclports.Log('Exctacting %s...' % os.path.basename(tar_file))
   if subprocess.call(['tar', 'xf', tar_file]):
     raise naclports.Error('Error unpacking Emscripten SDK')
 
+  if link_name:
+    if os.path.exists(link_name):
+      os.remove(link_name)
+    os.symlink(target_dir, link_name)
+
+
+def BuildOptimizer():
+  emsdk_root = os.path.join(OUT_DIR, 'emsdk')
+  node_bin = os.path.join(OUT_DIR, 'node', 'bin')
+  emscripten_root = os.path.join(emsdk_root, 'emscripten')
+  os.environ['EMSDK_ROOT'] = emscripten_root
+  os.environ['EM_CONFIG'] = os.path.join(emsdk_root, '.emscripten')
+  os.environ['PATH'] += ':' + node_bin
+  os.environ['PATH'] += ':' + emscripten_root
+
+  # Run using -O2 to compile the native js-optimizer
+  open('test.c', 'w').close()
+  subprocess.check_call(['emcc', '-O2', '-o', 'test.js', 'test.c'])
+  os.remove('test.js')
+  os.remove('test.c')
+  return 0
+
 
 def main(argv):
   if sys.platform in ['win32', 'cygwin']:
     naclports.Error('Emscripten support is currently not available on Windows.')
     return 1
 
   DownloadAndExtract(EMSDK_URL, EMSDK_SHA1, 'emsdk')
-  DownloadAndExtract(NODEJS_URL, NODEJS_SHA1, 'node-v0.12.1-linux-x64')
+  DownloadAndExtract(NODEJS_URL, NODEJS_SHA1, 'node-v0.12.1-linux-x64', 'node')
+  BuildOptimizer()
+
   naclports.Log('Emscripten SDK Install complete')
   return 0
 
 
 if __name__ == '__main__':
   try:
     rtn = main(sys.argv[1:])
   except naclports.Error as e:
     sys.stderr.write('error: %s\n' % str(e))
     rtn = 1