ci: install solana cli for anchor test

Added a step to install Solana CLI v1.18.26 in .github/workflows/build.yml.
This provides the `cargo-build-sbf` command required by `anchor test`.

Co-authored-by: ethan-hurst <23321960+ethan-hurst@users.noreply.github.com>

Author: google-labs-jules[bot]

.github/workflows/build.yml

@@ -19,6 +19,11 @@ jobs:
           target: x86_64-unknown-linux-gnu
           override: true
 
+      - name: Install Solana CLI
+        run: |
+          sh -c "$(curl -sSfL https://release.solana.com/v1.18.26/install)"
+          echo "/home/runner/.local/share/solana/install/active_release/bin" >> $GITHUB_PATH
+
       - name: Install Anchor
         run: |
           cargo install --git https://github.com/coral-xyz/anchor --tag v0.31.1 anchor-cli --locked