Bump Fuchsia versions

This updates the Fuchsia commit used in `auto - x86_64-gnu-integration`
CI bot to use the Rust commit 703dc9ce64.
This should help improve the coverage of this builder.

It also updates the SDK version to F20.20240412.3.1, and the Fuchsia Clang
version to c777c011a709dffd4fa5e79cad7947b7c3405d02.

src/ci/docker/host-x86_64/x86_64-gnu-integration/build-fuchsia.sh

@@ -5,7 +5,7 @@
 
 set -euf -o pipefail
 
-INTEGRATION_SHA=56310bca298872ffb5ea02e665956d9b6dc41171
+INTEGRATION_SHA=1011e3298775ee7cdf6f6dc73e808d6a86e33bd6
 PICK_REFS=()
 
 checkout=fuchsia

src/ci/docker/scripts/build-fuchsia-toolchain.sh

@@ -4,13 +4,13 @@ set -ex
 source shared.sh
 
 FUCHSIA_SDK_URL=https://chrome-infra-packages.appspot.com/dl/fuchsia/sdk/core/linux-amd64
-FUCHSIA_SDK_ID=MrhQwtmP8CpZre-i_PNOREcThbUcrX3bA-45d6WQr-cC
-FUCHSIA_SDK_SHA256=32b850c2d98ff02a59adefa2fcf34e44471385b51cad7ddb03ee3977a590afe7
+FUCHSIA_SDK_ID=version:20.20240412.3.1
+FUCHSIA_SDK_SHA256=cc52f3497487dd813c89d9316e6967efcea89c7759edccf3e40fcf3662e53f19
 FUCHSIA_SDK_USR_DIR=/usr/local/core-linux-amd64-fuchsia-sdk
 CLANG_DOWNLOAD_URL=\
 https://chrome-infra-packages.appspot.com/dl/fuchsia/third_party/clang/linux-amd64
-CLANG_DOWNLOAD_ID=Tpc85d1ZwSlZ6UKl2d96GRUBGNA5JKholOKe24sRDr0C
-CLANG_DOWNLOAD_SHA256=4e973ce5dd59c12959e942a5d9df7a19150118d03924a86894e29edb8b110ebd
+CLANG_DOWNLOAD_ID=git_revision:c777c011a709dffd4fa5e79cad7947b7c3405d02
+CLANG_DOWNLOAD_SHA256=779167422ad73c292f049dcea5569f84577af9292189ed2749518b966a4d0844
 
 install_clang() {
   mkdir -p clang_download

src/ci/docker/scripts/fuchsia-test-runner.py

@@ -280,7 +280,7 @@ class TestEnvironment:
         # Look up the product bundle transfer manifest.
         self.log_info("Looking up the product bundle transfer manifest...")
         product_name = "minimal." + self.triple_to_arch(self.target)
-        fuchsia_version = "14.20230811.2.1"
+        fuchsia_version = "20.20240412.3.1"
 
         # FIXME: We should be able to replace this with the machine parsable
         # `ffx --machine json product lookup ...` once F15 is released.