ci: fuzz: clean up fuzzer script a bit

scripts/atom_parser_fuzz.sh

@@ -0,0 +1,15 @@
+#!/bin/bash
+
+in=$(mktemp -u) || exit $?
+out=$(mktemp -u) || exit $?
+
+mkfifo ${in} ${out} || exit $?
+
+./scripts/atom.py <${in} >${out} \
+    | ./build/fuzz/atom/parser/fuzzer >${in} <${out} \
+                                      ./build/atom_parser_fuzzer_corpus \
+                                      -max_total_time=${FUZZER_TIMEOUT_S:-600} \
+                                      -only_ascii=1 \
+                                      -timeout=2 \
+                                      -timeout_exitcode=0 \
+                                      "$@"