[LyX/master] autotools: use system boost by default

[Enrico Forestieri]

On Sun, Nov 29, 2020 at 09:38:38PM +0100, Jean-Marc Lasgouttes wrote:
> commit ca938c08d9d110226f2c0133e304914f9cc83533
> Author: Jean-Marc Lasgouttes <lasgouttes at lyx.org>
> Date:   Sun Nov 29 22:07:26 2020 +0100
> 
>     autotools: use system boost by default
>     
>     What is missing is a test to use bundled boost automatically when
>     system boost is missing. I am not sure this is required, though.

It is required, otherwise configuration is successful but compilation fails:

  CXX      os.o
../../../src/support/checksum.cpp:13:10: fatal error: boost/crc.hpp: No such file or directory
   13 | #include "boost/crc.hpp"
      |          ^~~~~~~~~~~~~~~
compilation terminated.

So, either warn at the end of configuration that compilation is going
to fail, or automatically switch to included boost.

-- 
Enrico