This document describes how libcmark-gfm was packaged for build2. In
particular, this understanding will be useful when upgrading to a new upstream
version. See ../README-DEV for general notes on cmark-gfm packaging.

Symlink the required upstream files and directories into libcmark-gfm/:

$ ln -s ../../upstream/src libcmark-gfm

Note that we unable to generate cmark-gfm_version.h directly from the template
as it is included as "cmark-gfm_version.h" in upstream's source code, which
makes impossible using the header-generating machinery. That's why we create
libcmark-gfm/cmark-gfm_version.h that includes <libcmark-gfm/version.h> that
we auto-generate from upstream's src/cmark-gfm_version.h.in.

Use libcmark-gfm/config.h.in.orig for creating libcmark-gfm/config.h,
defining/undefining macros introduced with #cmakedefine.

Create cmark-gfm_export.h defining CMARK_GFM_EXPORT macro.