Revert "[fuchsia] Reland "Generate BUILD.gn from SDK metadata...""

This reverts commit 386fa9a70028f97ce511bc7bf84e5ce96e47f926.

Reason for revert:
Broke the fuchsia_sdk update step, see bug.

Original change's description:
> [fuchsia] Reland "Generate BUILD.gn from SDK metadata..."
> 
> Reland of CL https://chromium-review.googlesource.com/c/chromium/src/+/1241842.
> (Confirmed that the code builds on Cast builders, and manually examined
> all references to targets under //third_party/fuchsia-sdk to verify
> that all FIDL targets have been modified to reference the new sdk/
> subdir.)
> 
> This script uses the metadata JSON files in the SDK to generate a
> BUILD.gn in //third_party/fuchsia-sdk/sdk. The build file is
> regenerated whenever a new SDK is downloaded using "gclient sync".
> 
> Only FIDL libraries are migrated for now. Additional metadata types can
> be migrated in followup CLs.
> 
> TBR=scottmg@chromium.org
> TBR=sky@chromium.org
> 
> Bug: 888753
> Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel;luci.chromium.try:linux_optional_gpu_tests_rel;luci.chromium.try:mac_optional_gpu_tests_rel;luci.chromium.try:win_optional_gpu_tests_rel
> Change-Id: I7ec714982cdfbb6f6ccd8fad3cd7cbb48af4eb1c
> Reviewed-on: https://chromium-review.googlesource.com/1246681
> Commit-Queue: Kevin Marshall <kmarshall@chromium.org>
> Reviewed-by: Kevin Marshall <kmarshall@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#594419}

TBR=kmarshall@chromium.org

Change-Id: I1a89a1c3d8223e6dd58e2a4b23f251eb96a7bba8
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 888753, 889839
Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel;luci.chromium.try:linux_optional_gpu_tests_rel;luci.chromium.try:mac_optional_gpu_tests_rel;luci.chromium.try:win_optional_gpu_tests_rel
Reviewed-on: https://chromium-review.googlesource.com/1249203
Reviewed-by: Hans Wennborg <hans@chromium.org>
Commit-Queue: Hans Wennborg <hans@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#594671}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 712b34569c5dad99d67ad7ade9e4c456f61a3de0
3 files changed