wsynth-dssi fails to cross build from source, because it ships a broken,
outdated, embedded copy of AM_PATH_GTK_2_0. The actual bug was #895002,
but wsynth-dssi happens to ship a copy of the bug. Since the bug is
fixed already, this report comes without a patch.

The debian policy discourages using embedded copies. Please remove your
copy. Failing that, please update it and register it with the security
tracker. Please refer to https://wiki.debian.org/EmbeddedCodeCopies for
more information on how to register your copy.

Helmut