package/mpd: affected by GCC PR libstdc++/64735

MPD uses `exception_ptr` from libstdc++ which is not available for
architectures affected by GCC PR libstdc++/64735.

Fixes:
http://autobuild.buildroot.net/results/552/552e0c4d6482b60045a91fd398c4ffecd8877cce/
http://autobuild.buildroot.net/results/4d3/4d384950b6dba21163bdcd7721ddad133beeb72b/
http://autobuild.buildroot.net/results/842/842e992315dd78765938e6b629386a18fa9bb00c/


.. and many more.

Signed-off-by: Jörg Krause <joerg.krause@embedded.rocks>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>