Roll Fuchsia SDK from 4cb6cfe20aa2 to 668b00d3344a

The AutoRoll server is located here: https://autoroll.skia.org/r/fuchsia-sdk-chromium-autoroll

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+/master/autoroll/README.md

If the roll is causing failures, please contact the current sheriff, who should
be CC'd on the roll, and stop the roller if necessary.


CQ_INCLUDE_TRYBOTS=luci.chromium.try:fuchsia-arm64-cast;luci.chromium.try:fuchsia-x64-cast
TBR=cr-fuchsia+bot@chromium.org

Change-Id: Ic4422602a4dab51f54a2d1a87fdcd827cc38d8ea
Reviewed-on: https://chromium-review.googlesource.com/c/1394367Reviewed-by: chromium-autoroll <chromium-autoroll@skia-public.iam.gserviceaccount.com>
Commit-Queue: chromium-autoroll <chromium-autoroll@skia-public.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/master@{#619592}

build/fuchsia/linux.sdk.sha1

-4cb6cfe20aa2144b34d051ee31306969be7582c7
+668b00d3344a035008219c70b4b6ed459305d720
\ No newline at end of file

build/fuchsia/mac.sdk.sha1

-ece0fa0dc069c87a2ce7636fc4b170de33642d05
+979d8a9d0895514851d9960670793a1aa9a5c537
\ No newline at end of file