Build GCC with the following options to get a good libstd++ build.

The --with-cpu line appears to the critical line.  Without, there are futex symbols missing from
libstdc++ resulting in llvm build/linker errors.  And don't disable bootstrap, as that appears to break
it too.


CC="gcc -mtune=arm1176jzf-s -mfpu=vfp -march=armv6zk -Os" \
CXX="g++ -mtune=arm1176jzf-s -mfpu=vfp -march=armv6zk -Os" \
../configure --prefix=/usr/local --enable-languages=c,c++ --enable-default-pie --enable-default-ssp \
--disable-multilib --with-system-zlib --libexecdir=/usr/local/lib \
--with-isl=/usr/local \
--with-mpfr=/usr/local \
--with-gmp=/usr/local \
--with-mpc=/usr/local \
--enable-lto \
--with-pkgversion=piCore \
--with-cpu=arm1176jzf-s --with-float=hard --with-fpu=vfp