This blog is updated daily.
A general description is here.
zip.unpack() (deprecated in R 2.13.0) is defunct: use ‘unzip()’ instead.
There is preliminary support for ‘multilib’ toolchains which use options ‘--m32’ or ‘--m64’ to select the architecture; set the appropriate macros in ‘MkRules.local’.
It is the intention to move to such a toolchain when they become mature enough.