title: gdb script: How can a script determine if it is invoked under `gdb` or `gdb-multiarch`?
body: <p>I'd like to define a command which does X under <code>gdb-multiarch</code>, but prints out a helpful message when run under normal <code>gdb</code>.  How can my script determine which of the two its run under?</p>
  <p>Why? When I start gdb-multiarch, I can bind to a qemu-arm session.  When I try that in gdb, I get bizarre errors.  It's easy to forget and run gdb (and not -multiarch), and I want to my <code>bind-to-qemu</code> tell me &quot;This must be run under gdb-multiarch&quot;.</p>