Limit emulator tests to single thread.
Limit emulator tests to single thread.

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