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FLASHING.md says how to take a newer version of the colleague's tree (copy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/gpsnc.sh

@@ -0,0 +1,25 @@
+#!/bin/sh
+GPSD_LOCAL_PORT=8051
+NMEA_REMOTE_PORT=8052
+NC_REMOTE_PID=0
+NC_LOCAL_PID=0
+FIFO=/tmp/gpsnc_fifo.$$
+
+exit_handler()
+{
+    kill $NC_REMOTE_PID 2>/dev/null
+    kill $NC_LOCAL_PID 2>/dev/null
+    rm -f $FIFO
+}
+
+trap exit_handler SIGINT SIGTERM
+
+mkfifo $FIFO
+nc -k -l ${NMEA_REMOTE_PORT} > $FIFO &
+NC_REMOTE_PID=$!
+nc -l ${GPSD_LOCAL_PORT} < $FIFO &
+NC_LOCAL_PID=$!
+
+sleep 1 # wait for nc ports becoming available
+gpsd -n -N -D4 tcp://localhost:${GPSD_LOCAL_PORT}
+