Port AFL stuff from zcash upstream

zcutil/afl/afl-getbuildrun.sh

@@ -0,0 +1,20 @@
+#!/usr/bin/env bash
+# Builds AFL and an instrumented zcashd, then begins fuzzing.
+# This script must be run from within the top level directory of a zcash clone.
+# Pass it the name of a directory in ./src/fuzzing.
+# Additional arguments are passed-through to AFL.
+
+set -eu -o pipefail
+
+FUZZ_CASE="$1"
+shift 1
+
+export AFL_INSTALL_DIR=$(realpath "./afl-temp")
+
+if [ ! -d "$AFL_INSTALL_DIR" ]; then
+    mkdir "$AFL_INSTALL_DIR"
+    ./zcutil/afl/afl-get.sh "$AFL_INSTALL_DIR"
+fi
+
+./zcutil/afl/afl-build.sh "$AFL_INSTALL_DIR" "$FUZZ_CASE" -j$(nproc)
+./zcutil/afl/afl-run.sh "$AFL_INSTALL_DIR" "$FUZZ_CASE" "$@"