Changelog r13 beta1

Changelog

Report issues to GitHub.

NDK_TOOLCHAIN_VERSION now defaults to Clang.
libc++ has been updated to r263688.
- We've reset to a (nearly) clean upstream. This should remove a number of bugs, but we still need to clean up libandroid_support before we will recommend it as the default.
make-standalone-toolchain.sh is now simply a wrapper around the Python version of the tool. There are a few behavioral differences. See https://android-review.googlesource.com/#/c/245453/
Some libraries for unsupported ABIs have been removed (mips64r2, mips32r6, mips32r2, and x32). There might still be some stragglers.
Issues with crtbegin_static.o that resulted in missing atexit at link time when building a static executable for ARM android-21+ have been resolved: https://github.com/android-ndk/ndk/issues/132

This is not intended to be a comprehensive list of all outstanding bugs.
Standlone toolchains using libc++ and GCC do not work. This seems to be a bug in GCC. See the following commit message for more details: https://android-review.googlesource.com/#/c/247498
x86 ASAN still does work. See discussion on https://android-review.googlesource.com/#/c/186276/
Exception unwinding with c++_shared still does not work for ARM on Gingerbread or Ice Cream Sandwich.
Bionic headers and libraries for Marshmallow and N are not yet exposed despite the presence of android-24. Those platforms are still the Lollipop headers and libraries (not a regression from r11).
RenderScript tools are not present (not a regression from r11): https://github.com/android-ndk/ndk/issues/7.