ci: don't run full fuzz corpora

Our corpora are too large to run in full on every pull request, they just take
too long. Instead, we sample some of them and make sure that running our fuzzers
over the sampled inputs still works OK.

Author: fitzgen

.github/workflows/main.yml

@@ -79,15 +79,33 @@ jobs:
     - uses: ./.github/actions/install-rust
       with:
         toolchain: nightly
-    - run: cargo install cargo-fuzz
+    - run: cargo install cargo-fuzz --vers "^0.6"
     - run: cargo fetch
       working-directory: ./fuzz
-    # NB: the `-runs=0` means that libFuzzer won't generate new inputs, only run
-    # the seeds from the corpus.
-    - run: cargo fuzz run compile                --release --debug-assertions -- -runs=0
-    - run: cargo fuzz run instantiate            --release --debug-assertions -- -runs=0
-    - run: cargo fuzz run instantiate_translated --release --debug-assertions -- -runs=0
-    - run: cargo fuzz run api_calls              --release --debug-assertions -- -runs=0
+    - run: cargo fuzz build --release --debug-assertions
+    # Our corpora are too large to run in full on every pull request, they just
+    # take too long. Instead, we sample some of them and make sure that running
+    # our fuzzers over the sampled inputs still works OK.
+    - run: |
+        find fuzz/corpus/compile -type f \
+            | shuf \
+            | head -n 3000 \
+            | xargs cargo fuzz run compile --release --debug-assertions
+    - run: |
+        find fuzz/corpus/instantiate -type f \
+            | shuf \
+            | head -n 2000 \
+            | xargs cargo fuzz run instantiate --release --debug-assertions
+    - run: |
+        find fuzz/corpus/instantiate_translated -type f \
+            | shuf \
+            | head -n 1000 \
+            | xargs cargo fuzz run instantiate_translated --release --debug-assertions
+    - run: |
+        find fuzz/corpus/api_calls -type f \
+            | shuf \
+            | head -n 100 \
+            | xargs cargo fuzz run api_calls --release --debug-assertions
 
   # Install wasm32-unknown-emscripten target, and ensure `crates/wasi-common`
   # compiles to Emscripten.