Fix x86_64 compilation on Ubuntu 14.04

* Add necessary includes in bt_trace.h
* Add toolchain specific configs
* Add libc++ import for clang
* Add libc++abi include for clang
* Add ipc_handler_linux.cc in service/BUILD.gn
* Use shared_mutex when _LIBCPP_VERSION < 3500
* Updated the build instructions

Test: ninja -C out/Default
Change-Id: I362ebf33f62910be817339cc6bdc62830f57db30