It was failing to generate doc with recent version of gtk-doc
[kmod]$ ./bootstrap
libkmod/docs/gtk-doc.make:33: error: EXTRA_DIST must be set with '=' before using '+='
libkmod/docs/Makefile.am:29: 'libkmod/docs/gtk-doc.make' included from here
autoreconf: automake failed with exit status: 1
Just add an empty EXTRA_DIST so it works.
These redirecting makefiles simplifies compiling from some editors and
when CWD is not the root of the source tree. This is similar to what was
introduced in systemd in 340d89e ("build-sys: add small redirecting
Makefiles to simplify compilation from within emacs")
Current limitation is horrible no support to sections: we have to to
have separate header files or to maintain the libkmod-sections.txt file.
We are doing the latter.