feat(scripts: debug): add a script to start a debug session

Since switching to a higher-half kernel, placing the "target remote ..."
inside the gdbinit script seems to make GDB crash. Having it executed
as a CLI argument seems to be a working alternative.

This script lets us chose which symbol we want to set a breakpoint on,
instead of hardcoding it to kernel_main inside the gdbinit script.

.gdbinit

@@ -1,9 +1 @@
-# Connect to qemu's gdbserver
-target remote :1234
-
-# Change layout
-layout reg
-
-# Continue execution until entering the kernel
-break kernel_main
-continue
+layout src

scripts/debug.sh

@@ -0,0 +1,39 @@
+#!/usr/bin/env bash
+
+# Start a GDB session connected to our kernel.
+# You can also pass in symbols to set breakpoints on as arguments.
+#
+# example: ./debug.sh kernel_main mmu_init
+
+# Absolute path to this script
+SCRIPT=$(readlink -f "$0")
+SCRIPTDIR=$(dirname "$SCRIPT")
+GITROOT="$SCRIPTDIR/.."
+
+if ! command -v gdb > /dev/null; then
+    echo "[ERROR] GDB not found in path" >&2
+    exit 127
+fi
+
+cd "$GITROOT" || exit
+
+BREAKPOINTS=()
+for symbol in "$@"; do
+    BREAKPOINTS+=("-ex" "break $symbol")
+done
+
+if [ ! -d "build" ]; then
+    echo "[INFO] build dir not found, setting up meson project"
+    meson setup build --cross-file "scripts/meson_cross.ini" --reconfigure -Dbuildtype=debug
+fi
+
+echo "[INFO] Starting a debugging session"
+ninja -C build qemu-server || exit
+gdb -x .gdbinit --symbol ./build/kernel/kernel.sym \
+    -iex "set pagination of" \
+    -iex "target remote localhost:1234" \
+    "${BREAKPOINTS[@]}" \
+    -ex "continue"
+
+echo "[INFO] Terminating debugging session"
+pkill qemu