Refactor BUILD file.
Refactor BUILD file.

petewarden/gemmlowp,efeguney/gemmlowp,maciekcc/gemmlowp,petewarden/gemmlowp,google/gemmlowp,efeguney/gemmlowp,google/gemmlowp,maciekcc/gemmlowp,google/gemmlowp,maciekcc/gemmlowp,petewarden/gemmlowp,google/gemmlowp,efeguney/gemmlowp,petewarden/gemmlowp