Fix WebRTC API framework build.

BUG=webrtc:5737

Review URL: https://codereview.webrtc.org/1875003004

Cr-Commit-Position: refs/heads/master@{#12391}
diff --git a/webrtc/build/ios/merge_ios_libs.py b/webrtc/build/ios/merge_ios_libs.py
new file mode 100755
index 0000000..651024e
--- /dev/null
+++ b/webrtc/build/ios/merge_ios_libs.py
@@ -0,0 +1,124 @@
+#!/usr/bin/python
+
+#  Copyright 2016 The WebRTC project authors. All Rights Reserved.
+#
+#  Use of this source code is governed by a BSD-style license
+#  that can be found in the LICENSE file in the root of the source
+#  tree. An additional intellectual property rights grant can be found
+#  in the file PATENTS.  All contributing project authors may
+#  be found in the AUTHORS file in the root of the source tree.
+
+"""Script for merging generated iOS libraries."""
+
+import sys
+
+import argparse
+import os
+import re
+import subprocess
+
+# Valid arch subdir names.
+VALID_ARCHS = ['arm_libs', 'arm64_libs', 'ia32_libs', 'x64_libs']
+
+
+def MergeLibs(lib_base_dir):
+  """Merges generated iOS libraries for different archs.
+
+  Uses libtool to generate FAT archive files for each generated library.
+
+  Args:
+    lib_base_dir: directory whose subdirectories are named by architecture and
+                  contain the built libraries for that architecture
+
+  Returns:
+    Exit code of libtool.
+  """
+  output_dir_name = 'fat_libs'
+  archs = [arch for arch in os.listdir(lib_base_dir)
+           if arch in VALID_ARCHS]
+  # For each arch, find (library name, libary path) for arch. We will merge
+  # all libraries with the same name.
+  libs = {}
+  for lib_dir in [os.path.join(lib_base_dir, arch) for arch in VALID_ARCHS]:
+    if not os.path.exists(lib_dir):
+      continue
+    for dirpath, _, filenames in os.walk(lib_dir):
+      for filename in filenames:
+        if not filename.endswith('.a'):
+          continue
+        entry = libs.get(filename, [])
+        entry.append(os.path.join(dirpath, filename))
+        libs[filename] = entry
+  orphaned_libs = {}
+  valid_libs = {}
+  for library, paths in libs.items():
+    if len(paths) < len(archs):
+      orphaned_libs[library] = paths
+    else:
+      valid_libs[library] = paths
+  for library, paths in orphaned_libs.items():
+    components = library[:-2].split('_')[:-1]
+    found = False
+    # Find directly matching parent libs by stripping suffix.
+    while components and not found:
+      parent_library = '_'.join(components) + '.a'
+      if parent_library in valid_libs:
+        valid_libs[parent_library].extend(paths)
+        found = True
+        break
+      components = components[:-1]
+    # Find next best match by finding parent libs with the same prefix.
+    if not found:
+      base_prefix = library[:-2].split('_')[0]
+      for valid_lib, valid_paths in valid_libs.items():
+        if valid_lib[:len(base_prefix)] == base_prefix:
+          valid_paths.extend(paths)
+          found = True
+          break
+    assert found
+
+  # Create output directory.
+  output_dir_path = os.path.join(lib_base_dir, output_dir_name)
+  if not os.path.exists(output_dir_path):
+    os.mkdir(output_dir_path)
+
+  # Use this so libtool merged binaries are always the same.
+  env = os.environ.copy()
+  env['ZERO_AR_DATE'] = '1'
+
+  # Ignore certain errors.
+  libtool_re = re.compile(r'^.*libtool:.*file: .* has no symbols$')
+
+  # Merge libraries using libtool.
+  libtool_returncode = 0
+  for library, paths in valid_libs.items():
+    cmd_list = ['libtool', '-static', '-v', '-o',
+                os.path.join(output_dir_path, library)] + paths
+    libtoolout = subprocess.Popen(cmd_list, stderr=subprocess.PIPE, env=env)
+    _, err = libtoolout.communicate()
+    for line in err.splitlines():
+      if not libtool_re.match(line):
+        print >>sys.stderr, line
+    # Unconditionally touch the output .a file on the command line if present
+    # and the command succeeded. A bit hacky.
+    libtool_returncode = libtoolout.returncode
+    if not libtool_returncode:
+      for i in range(len(cmd_list) - 1):
+        if cmd_list[i] == '-o' and cmd_list[i+1].endswith('.a'):
+          os.utime(cmd_list[i+1], None)
+          break
+  return libtool_returncode
+
+
+def Main():
+  parser_description = 'Merge WebRTC libraries.'
+  parser = argparse.ArgumentParser(description=parser_description)
+  parser.add_argument('lib_base_dir',
+                      help='Directory with built libraries. ',
+                      type=str)
+  args = parser.parse_args()
+  lib_base_dir = args.lib_base_dir
+  MergeLibs(lib_base_dir)
+
+if __name__ == '__main__':
+  sys.exit(Main())