build: support ARM with meson

build: support ARM with meson

Add files to enable compiling for ARM native/cross builds.
This can be tested by doing a cross-compile for armv8-a type using
the linaro gcc toolchain.

        meson arm-build --cross-file aarch64_cross.txt
        ninja -C arm-build

where aarch64_cross.txt contained the following

        [binaries]
        c = 'aarch64-linux-gnu-gcc'
        cpp = 'aarch64-linux-gnu-cpp'
        ar = 'aarch64-linux-gnu-ar'

        [host_machine]
        system = 'linux'
        cpu_family = 'aarch64'
        cpu = 'armv8-a'
        endian = 'little'

Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
Signed-off-by: Pavan Nikhilesh <pbhagavatula@caviumnetworks.com>
Acked-by: Jerin Jacob <jerin.jacob@caviumnetworks.com>