data-to-c is part of the build system, generating header files from binary data. However, it is currently written in C and thus when cross compiling, the executable is produced for the _target_ platform, which the host is usually unable to run.

Some other helpers like glib-genmarshal are installed by the native build and it's possible to use e.g. /usr/bin/glib-genmarshal for the cross build. But that approach doesn't work for data-to-c because it's an internal helper and not installed during make install.