Build libwebrtc using libcxx. Set use_custom_libcxx=0. According to the
source comment, use_custom_libcxx=1 means to use a precompiled libcxx in
the third_party directory.

Build the test target
obj/webrtc/api/test/peerconnection_unittests.fakeaudiocapturemodule.o
rather than peerconnection_unittests.isolated; building just an object
file doesn't require the linker and is faster.

Use x86_64-apple-darwin11-ar, not ar, to link libwebrtc-magic.a.
When linking go-webrtc later on, it would cause the error:
ld: warning: ignoring file lib/libwebrtc-darwin-amd64-magic.a, file was built for archive which is not the architecture being linked (x86_64)

Descriptions for each patch are in the mbox-formatted patch file.

Subject: [PATCH 01/13] Use flags for GNU grep, not BSD grep.
Subject: [PATCH 02/13] Remove flags not supported by Mac ld.
Subject: [PATCH 03/13] Undefine __APPLE__ in usrsctp.
Subject: [PATCH 04/13] Include <sys/socket.h> in macifaddrs_converter.cc.
Subject: [PATCH 05/13] Allow non-mac to build .m and .mm sources (objc and
Subject: [PATCH 06/13] Propagate "-framework Foundations" in ldflags.
Subject: [PATCH 07/13] Provide definitions of NS_ENUM and NS_OPTIONS.
Subject: [PATCH 08/13] Remove lightweight-generics annotations from NSArray
Subject: [PATCH 09/13] Use -fobjc-arc in webrtc/build/objc_common.gypi.
Subject: [PATCH 10/13] Replace firstObject with objectAtIndex:0.
Subject: [PATCH 11/13] fobjc-arc
Subject: [PATCH 12/13] Use objectAtIndex instead of array index syntax.
Subject: [PATCH 13/13] Hack out some more NS_ENUM and NS_OPTIONS.

As in ab1e5cffbf548f9f586b81928dc22ae90bdec374 for linux.

Update the "$(SDKROOT)" replacement command. Use our own $SDKROOT as the
replacement. Files are now found in additional subdirectories.

The webrtc source extensively uses symlinks, which the "tar -h" in
copy-to-target flattens into duplicate files. Also, the tarball
(omitting .git history) is way smaller than the full source tree (1.5 GB
compared to 13 GB).

This is needed for cross-compilation of libwebrtc for mac.

http://public.kitware.com/Bug/view.php?id=14603
http://public.kitware.com/Bug/file_download.php?file_id=4981&type=bug

The first public release of cmake that has this fix is v3.0.0.

Without this, setting CMAKE_SYSTEM_NAME=Darwin results in errors:

-- The CXX compiler identification is Clang 3.8.0
-- The C compiler identification is Clang 3.8.0
CMake Error at /home/debian/install/cmake/share/cmake-2.8/Modules/Platform/Darwin.cmake:344 (list):
  list sub-command REMOVE_DUPLICATES requires list to be present.
Call Stack (most recent call first):
  /home/debian/install/cmake/share/cmake-2.8/Modules/CMakeSystemSpecificInformation.cmake:36 (include)
  CMakeLists.txt:15 (project)

-- Check for working CXX compiler: /home/debian/install/clang/bin/clang++
CMake Error at /home/debian/install/cmake/share/cmake-2.8/Modules/Platform/Darwin.cmake:344 (list):
  list sub-command REMOVE_DUPLICATES requires list to be present.
Call Stack (most recent call first):
  /home/debian/install/cmake/share/cmake-2.8/Modules/CMakeSystemSpecificInformation.cmake:36 (include)
  CMakeLists.txt:2 (PROJECT)

CMake Error: Internal CMake error, TryCompile configure of cmake failed
-- Check for working CXX compiler: /home/debian/install/clang/bin/clang++ -- broken
CMake Error at /home/debian/install/cmake/share/cmake-2.8/Modules/CMakeTestCXXCompiler.cmake:54 (message):
  The C++ compiler "/home/debian/install/clang/bin/clang++" is not able to
  compile a simple test program.

  It fails with the following output:

  CMake will not be able to correctly generate this project.
Call Stack (most recent call first):
  CMakeLists.txt:15 (project)

-- Configuring incomplete, errors occurred!
See also "/home/debian/build/libcxx/build/CMakeFiles/CMakeOutput.log".
See also "/home/debian/build/libcxx/build/CMakeFiles/CMakeError.log".