ci: use ASan/UBsan in bluetooth tests

Compile with sanitizers for the bluetooth tests, for better backtraces
on failures. Also produce backtraces via gdb.

.gitlab/ci/core-backtrace.sh

@@ -0,0 +1,22 @@
+#!/bin/sh
+#
+# core-backtrace.sh COREFILE...
+#
+# Print backtraces from core dump files
+#
+set -e
+
+for f in "$@"; do
+    if [ ! -e "$f" ]; then
+        continue
+    fi
+    echo "#"
+    echo "# --- $f ---"
+    echo "#"
+    exe=$(gdb -q -c "$f" -ex 'info auxv' -ex quit | sed -n -e '/AT_EXECFN/ { s/^[^"]*"//; s/"$//; p; }')
+    if [ -f "$exe" ]; then
+        gdb -q "$exe" "$f" -ex 'thr a a bt full' -ex quit
+    else
+        gdb -q -c "$f" -ex 'thr a a bt full' -ex quit
+    fi
+done