The target machine is represented by TARGET_ARCH. MACHINE_ARCH always
represents the host machine. When TARGET_ARCH is not defined, it is
assumed to be equal to MACHINE_ARCH. This means that we're building a
native toolset by default. We're creating cross-compilation tools when
MACHINE_ARCH != TARGET_ARCH.
TARGET_ARCH is defined when building binutils as part of the bootstrap
build and is set to reflect the architecture we're currently cross-
building. With this change binutils is ready for cross-building.
