Fix fuzzer executable detection in test_all. (#156)

Author: oliverchang

infra/base-images/base-runner/test_all

@@ -24,6 +24,10 @@ set -o pipefail
 
 N=0
 for FUZZER_BINARY in $(find $OUT/ -executable -type f); do
+  if file "$FUZZER_BINARY" | grep -v ELF > /dev/null 2>&1; then
+    continue
+  fi
+
   FUZZER=$(basename $FUZZER_BINARY)
   echo "testing $FUZZER"
   out=$(tempfile)