Detecting that AC_PROG_LIBTOOL has been invoked

[Benoit Sigoure]

Hello,
is it possible to detect that AC_PROG_LIBTOOL has been invoked,  
either at runtime by looking at a shell variable that Libtool defines  
or preferably at autoreconf-time by looking at one of the m4 macros  
it defines?  I'd like something that works on reasonably old versions  
of Libtool (like, 3 year old versions which I think you can still  
find out there).

The reason why I'm asking this is that I wrote some macros that rely  
on Libtool's magic handling of -R and even though it's clearly stated  
in the doc/comments/README that Libtool is mandatory, people keep  
running in troubles because they didn't use Libtool, so I'd like to  
trigger an error, somehow, to tell them that they did something wrong.

Cheers,

--
Benoit Sigoure aka Tsuna
EPITA Research and Development Laboratory