Update Rust before setting up the cache (#2460)

The cache is keyed on the Rust version used, so we should update Rust
before setting up the cache.

This is a small update to #2449.

.github/workflows/build.yml

@@ -52,12 +52,12 @@ jobs:
       - name: Checkout
         uses: actions/checkout@v4
 
-      - name: Setup Rust cache
-        uses: ./.github/workflows/setup-rust-cache
-
       - name: Update Rust
         run: rustup update
 
+      - name: Setup Rust cache
+        uses: ./.github/workflows/setup-rust-cache
+
       - name: Build Rust code
         run: cargo build
 
@@ -83,6 +83,11 @@ jobs:
       - name: Checkout
         uses: actions/checkout@v4
 
+      - name: Install toolchain
+        run: |
+          rustup update
+          rustup target add ${{ matrix.target }}
+
       - name: Setup Rust cache
         uses: ./.github/workflows/setup-rust-cache
 
@@ -91,11 +96,6 @@ jobs:
           sudo apt update
           sudo apt install gcc-aarch64-linux-gnu
 
-      - name: Install toolchain
-        run: |
-          rustup update
-          rustup target add ${{ matrix.target }}
-
       - name: Build Rust code
         working-directory: ${{ matrix.directory }}
         run: cargo build
@@ -135,6 +135,9 @@ jobs:
         with:
           fetch-depth: 0 # We need the full history for build.sh below.
 
+      - name: Update Rust
+        run: rustup update
+
       - name: Setup Rust cache
         uses: ./.github/workflows/setup-rust-cache
         with:
@@ -145,9 +148,6 @@ jobs:
           sudo apt update
           sudo apt install gettext
 
-      - name: Update Rust
-        run: rustup update
-
       - name: Install mdbook
         uses: ./.github/workflows/install-mdbook