Keep the colleague's microbu-esp32c5 tree in this repository

obu-firmware builds against vanetza-idf from microbu-esp32c5/external, but
that tree was gitignored, so a clone of this repository could not build the
firmware it ships. It is now committed here as ordinary files in its own
folder, microbu-esp32c5/: the colleague's commit cf4b99f plus the V2X2MAP
bridge's signature verification (--trust) used on the bench. Nothing is
fetched from or pushed to the colleague's repository; this repository and
its remotes carry everything. The folder's own .gitignore keeps build output,
downloaded components and private key material out, as it did there; the
committed file set is identical to that repository's tracked files.

The ESP32-C5 is still flashed from obu-firmware/, which only takes
vanetza-idf from microbu-esp32c5/, so the two stay separate folders.
FLASHING.md says how to take a newer version of the colleague's tree (copy
it over the folder, rebuild, test, commit).

microbu-esp32c5/external/vanetza-idf/tools/fuzz-harness/compile.sh

@@ -0,0 +1,25 @@
+#!/bin/bash
+set -eu
+
+if [[ ! -d "/AFLplusplus" ]] ; then
+    echo "This script shall be run inside the AFL++ container"
+    exit 1
+fi
+
+cd /home/fuzz
+
+export CC=${CC:=afl-clang-lto}
+export CXX=${CXX:=afl-clang-lto++}
+
+export AFL_LLVM_CMPLOG=1
+mkdir -p build/cmplog
+cmake -S source -B build/cmplog -G Ninja -DBUILD_FUZZ=ON
+cmake --build build/cmplog
+unset AFL_LLVM_CMPLOG
+
+# see https://aflplus.plus/docs/env_variables/ for supported environment variables
+export AFL_USE_ASAN=1
+export AFL_USE_UBSAN=1
+mkdir -p build/asan
+cmake -S source -B build/asan -G Ninja -DBUILD_FUZZ=ON
+cmake --build build/asan