fuzzing.yml: Reproducible toolchain setup (uutils#10487)

Author: oech3

.github/workflows/fuzzing.yml

@@ -58,15 +58,16 @@ jobs:
     - uses: actions/checkout@v6
       with:
         persist-credentials: false
-    - uses: dtolnay/rust-toolchain@nightly
     - name: Install `cargo-fuzz`
-      run: cargo install cargo-fuzz
+      run: |
+        echo "RUSTC_BOOTSTRAP=1" >> "${GITHUB_ENV}" # Use -Z
+        cargo install cargo-fuzz --locked
     - uses: Swatinem/rust-cache@v2
       with:
         shared-key: "cargo-fuzz-cache-key"
         cache-directories: "fuzz/target"
     - name: Run `cargo-fuzz build`
-      run: cargo +nightly fuzz build
+      run: cargo fuzz build
 
   fuzz-run:
     needs: fuzz-build
@@ -102,9 +103,10 @@ jobs:
     - uses: actions/checkout@v6
       with:
         persist-credentials: false
-    - uses: dtolnay/rust-toolchain@nightly
     - name: Install `cargo-fuzz`
-      run: cargo install cargo-fuzz
+      run: |
+        echo "RUSTC_BOOTSTRAP=1" >> "${GITHUB_ENV}" # Use nightly
+        cargo install cargo-fuzz --locked
     - uses: Swatinem/rust-cache@v2
       with:
         shared-key: "cargo-fuzz-cache-key"
@@ -122,7 +124,7 @@ jobs:
       run: |
         mkdir -p fuzz/stats
         STATS_FILE="fuzz/stats/${{ matrix.test-target.name }}.txt"
-        cargo +nightly fuzz run ${{ matrix.test-target.name }} -- -max_total_time=${{ env.RUN_FOR }} -timeout=${{ env.RUN_FOR }} -detect_leaks=0 -print_final_stats=1 2>&1 | tee "$STATS_FILE"
+        cargo fuzz run ${{ matrix.test-target.name }} -- -max_total_time=${{ env.RUN_FOR }} -timeout=${{ env.RUN_FOR }} -detect_leaks=0 -print_final_stats=1 2>&1 | tee "$STATS_FILE"
 
         # Extract key stats from the output
         if grep -q "stat::number_of_executed_units" "$STATS_FILE"; then