chore: add helper scripts

build.sh

@@ -0,0 +1,5 @@
+#!/bin/sh
+
+mkdir -p _build
+cmake -S . -B _build -D CMAKE_BUILD_TYPE=Debug
+cmake --build _build

run.sh

@@ -0,0 +1,3 @@
+#!/bin/sh
+
+gdb _build/igmpgen