ci: pin fuzz builds to the gnu target

Newer cargo-fuzz (as installed on the runner) defaults to
x86_64-unknown-linux-musl, whose statically linked libc is incompatible with
AddressSanitizer and is not installed on the runner anyway. Pin --target to
x86_64-unknown-linux-gnu, which uses a dynamic libc and ships with the nightly
toolchain. Document the same workaround in fuzz/README.md.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: maltesander

.github/workflows/build.yaml

@@ -122,10 +122,16 @@ jobs:
 
       # A short smoke run per target: long enough to shake out an ASAN overrun
       # in the pointer-marshalling paths, short enough for per-PR CI.
+      #
+      # --target is pinned to the gnu triple explicitly: newer cargo-fuzz
+      # defaults to x86_64-unknown-linux-musl, whose statically linked libc is
+      # incompatible with AddressSanitizer ("sanitizer is incompatible with
+      # statically linked libc"). gnu uses a dynamic libc and ships with the
+      # nightly toolchain.
       - name: Fuzz utf16
-        run: cargo +nightly fuzz run utf16 -- -max_total_time=30
+        run: cargo +nightly fuzz run utf16 --target x86_64-unknown-linux-gnu -- -max_total_time=30
       - name: Fuzz column_value
-        run: cargo +nightly fuzz run column_value -- -max_total_time=30
+        run: cargo +nightly fuzz run column_value --target x86_64-unknown-linux-gnu -- -max_total_time=30
 
   # Single required check for branch protection rules.
   finished:

fuzz/README.md

@@ -26,6 +26,14 @@ cargo +nightly fuzz run utf16
 cargo +nightly fuzz run column_value
 ```
 
+If cargo-fuzz fails with "sanitizer is incompatible with statically linked
+libc", it defaulted to a musl target; pin the gnu triple explicitly (this is
+what CI does):
+
+```bash
+cargo +nightly fuzz run utf16 --target x86_64-unknown-linux-gnu
+```
+
 `cargo fuzz run` runs **indefinitely** until it finds a crash or you stop it. To
 bound a run, pass a libFuzzer flag after `--`: