Enable bazel metrics from ninja build.

Generate the bazel profile file that contains the metrics of
executing the ninja build phase of Soong.

Bug: b/173028918
Test: * m nothing and check out dir that there is no bazel_metrics dir.
      * USE_BAZEL=1 m nothing and checked
        out/bazel_metrics/build_bazel_profile.gz existed.
      * m nothing and checked out/bazel_metrics does not exist.
Change-Id: I797d1eecf5c2c260ade8b55dc69c237bfd0fcbd4