Bazel 0.18 moved the workspace bazelrc location from //tools/bazel.rc to
//.bazelrc. The old location will be dropped by a future version of
bazel.
This bumps the minimum required version of bazel to 0.18.
More context:
https://groups.google.com/forum/#!msg/bazel-discuss/ycDacctX2vw/EGFxGLibAgAJ
PiperOrigin-RevId: 220338084
Change-Id: Ib6fa83a4a0f89e8e898d67152c7bd429e0b9b21e
Michael Pratt