mesa: check aarch64 system type as well (#14493)
mesa: check aarch64 system type as well (#14493)

to disabled use of libunwind.  Without this mesa fails to build
using recent Cray compilers - cce 9 and higher -  on aarch64 systems.

Signed-off-by: Howard Pritchard <7f27def7933aae48526941f79a37d0b5f7ece0e6@gmail.com>
LLNL/spack,iulian787/spack,iulian787/spack,LLNL/spack,iulian787/spack,LLNL/spack,iulian787/spack,LLNL/spack,iulian787/spack,LLNL/spack