Android buildbots: rename BuildSkDiff->BuildHostTools and do it in PreRender
Android buildbots: rename BuildSkDiff->BuildHostTools and do it in PreRender

This will allow us to run skimage on the buildslave host before the GenerateGMs
step, as noted in "step 1b" of https://goto.google.com/ChecksumTransitionDetail
(SkipBuildbotRuns)

This will require a master restart.

R=borenet@google.com

Review URL: https://codereview.chromium.org/16996003

git-svn-id: 32fc27f4dcfb6c0385cd9719852b95fe6680452d@9607 2bbb7eff-a529-9590-31e7-b0007b416f81

Tiger66639/skia-buildbot,google/skia-buildbot,google/skia-buildbot,Tiger66639/skia-buildbot,google/skia-buildbot,Tiger66639/skia-buildbot,google/skia-buildbot,google/skia-buildbot,Tiger66639/skia-buildbot,google/skia-buildbot,Tiger66639/skia-buildbot,Tiger66639/skia-buildbot,google/skia-buildbot,Tiger66639/skia-buildbot,google/skia-buildbot