This GCC patch was needed in order to successfully build a
cross-compilation toolchain under buildroot on Ubuntu 14.04.
The patch is included in later GCC releases, so we probably can drop
this once we upgrade GCC.
The GCC 4.6.x build system breaks when run on systems with sufficiently
recent versions of texinfo. Tweak buildroot configuration to avoid this
bug.
An equivalent workaround has been commited to buildroot (commit
62322ac). We can drop this once we upgrade buildroot and/or GCC.
GCC bug: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=60961
