Isolate the biggest CIPD assets to trim down on overhead

This change, when combined with https://skia-review.googlesource.com/c/buildbot/+/77701
should cut down on the duplicated work of extracting the large
toolchains from CIPD.

Since the Isolate* steps can be cached (i.e. are idempotent)
they will only run about 1/week (unless updated) and
all subsequent tasks (primarily Builds) will go much faster.

We estimate the overhead on Build-Debian-Android to go from
about 90s (which was more time than the actual build) to
about 10s.  Build-Win-Vulkan's overhead will improve from
about 180s to about 35s (1/3 of which is uploading to isolate).

Other CIPD assets could be handled in a similar fashion;
the ones here are the biggest offenders and the lowest
hanging fruit.  Doing this to other assets (e.g. clang_win)
would have minimal improvements (<10s).

There are other tasks with large amounts of overhead
(e.g. Build-Mac-Android, Build-Win-Android, Build-WASM)
but none of those are depended on by any Tests, so any
speed-ups would have less wide-reaching-impact, at the
cost of using more Isolate cache/diskspace.

See https://docs.google.com/document/d/1DFlcpqg7XqEPE5oYT1V3so2ih2285heS5w3mPT-GMBA/edit#
for more information.

Bug: skia:
Change-Id: I40dd87fe72c3d49292762a09dad6df0dfbe78f61
Reviewed-on: https://skia-review.googlesource.com/77560
Reviewed-by: Eric Boren <borenet@google.com>
Commit-Queue: Kevin Lubick <kjlubick@google.com>

0 files changed, 0 insertions, 0 deletions