Expose the binutils' machine name (typically used as a prefix on the
tool names) publicly. This is expected to match the `gcc -dumpmachine`
value.
Suggested-by: Ruslan Baratov <ruslan_baratov@yahoo.com>
CMake now supports cross compiling for Android using the NDK or a
standalone toolchain. Document the associated variables and how how to
write toolchain files for Android.