I've just pushed these:

  build: modernize bootstrap prerequsite tools
  Following Pádraig Brady's example from coreutils, ...
  * bootstrap.conf: Add an explicit requirement on m4.
  Add an explicit requirement on texi2pdf which is often packaged
  separately to makeinfo and induces a failure far down the
  distribution phase if not present.
  Replace the rsync dependency with wget,
  which gnulib changed to in 2018.
  Also, add an xz requirement and a version for autopoint.

  build: fix a new syntax-check failure
  * src/diff.h (robust_output_style): Put DIFF_INLINE and
  the function name on the same line, so that syntax-check's
  naive parsing can spot this function.
  * cfg.mk (_gl_TS_extern): Add DIFF_INLINE.