Fix cross- linux-tools build

cross-building the kernel with sbuild --host or apt-get build-dep -aarmhf && dpkg-buildpackage -aarmhf does not work. The kernel part is OK but the tools package build falls over.

There were various reasons for this.

First the cross-build-deps do not install because binutils-dev:armhf is a) not multiarch and b) not installable if it was due to binutils not being multiarched. This is being worked on (see http://lists.debian.org/debian-embedded/2013/01/msg00011.html). In the meantime we can install build-deps manually and proceed.
apt-get install debhelper cpio module-init-tools kernel-wedge rsync dpkg util-linux flex bison openssl libelf-dev:armhf libnewt-dev:armhf libdw-dev:armhf libunwind8-dev:armhf libaudit-dev:armhf
(and crossbuild-essential-armhf, or otherwise get a cross-toolchain)

The kernel cross build failed due to no arch being specified for the tools build so the wrong headers were found.

Also install -s is used, which uses the wrong strip. It might be better to refactor this to use dh_install which would DTRT, but for now I added --strip-program $(STRIP) and set $(STRIP) correctly for each call.
These fixes are in the first patch

This gives a working build, but none of the optional libraries are detected and used (libdw, libunwind, libaudit, libnewt). This is fixed by using the crosscompiler to run the tests when crossing, and adding config for arm for libunwind.
This fix is included in the -3 patch

C++ demangling support (via libiberty) won't work untilt there is a way to install bintuils-dev:armhf or equivalent.

Attached is also a version of the patch (-2) which includes a rename from 'build_arch' to 'kernel_arch' in the debian* arch-specific rules config, as 'build_arch' (reffering to the HOST_ARCH) is hopelessly confusing in a cross-build context. Agreed with Ubuntu upstream to use 'kernel_arch' instead.

Sorry this isn't a nice quilt set, but you get the idea.