The second test rebuild of Xenial Xerus was started in late February for all architectures, all components (it is finished besides some pending builds for powerpc and armhf).
Results (please also look at the superseded builds) can be found at
http://people.ubuntuwire.org/~wgrant/rebuild-ftbfs-test/test-rebuild-2016022...
For arm64 and armhf the gcc-5 packages are based on the Linaro 5-2016.02 snapshot.
Additional build failures for packages in xenial-proposed (not yet in xenial) can be found at http://qa.ubuntuwire.com/ftbfs/
Please help fixing the build failures.
Matthias
PS: Another test rebuild (using a snapshot of GCC 6) is built in preparation of the move to GCC 6 in 16.10. This can be found at http://people.ubuntuwire.org/~wgrant/rebuild-ftbfs-test/test-rebuild-2016022...
The corresponding compiler packages are in the PPA https://launchpad.net/~ubuntu-toolchain-r/+archive/ubuntu/test/
... just in case you want to make packages ready for GCC 6.