readme: factor out hardcoded paths on code snippets with getvar

getvar

@@ -0,0 +1,40 @@
+#!/usr/bin/env bash
+. "$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)/common"
+while getopts ha:gL:M:N:n:Q:t: OPT; do
+  case "$OPT" in
+    h)
+      echo "https://github.com/cirosantilli/linux-kernel-module-cheat#getvar" 2>&1
+      exit 0
+      ;;
+    a)
+      common_arch="$OPTARG"
+      ;;
+    g)
+      common_gem5=true
+      ;;
+    L)
+      common_linux_variant="$OPTARG"
+      ;;
+    M)
+      common_gem5_variant="$OPTARG"
+      ;;
+    N)
+      common_gem5_worktree="$OPTARG"
+      ;;
+    n)
+      common_run_id="$OPTARG"
+      ;;
+    Q)
+      common_qemu_variant="$OPTARG"
+      ;;
+    t)
+      common_gem5_build_type="$OPTARG"
+      ;;
+    ?)
+      exit 2
+      ;;
+  esac
+done
+shift "$(($OPTIND - 1))"
+common_setup
+eval "echo \$common_${1}"