Trying to install library(ffi), I get an error saying source_sink pack_build_path(autoheader)’ does not exist`.
My understand is that this is due to the legacy build system the pack is using…is there a simple fix?
You need to install autoconf. Probably time to move it to CMake. I’m still a bit in doubt about this package. The main issue is that parsing C should not be so hard, but compilers tend to have all sorts of extensions that are used in the system header files. Typically it is mostly stuff that can be ignored, but you have to extend the grammar 
It is just hard to remain compatible with each new C compiler version. Notably MacOS is a moving target …
Another source of trouble is that it is not uncommon that the documented API function is a macro or inline function that calls something else. That is rather hard to deal with
Hm, strange, I do have autoconf installed; perhaps the build system is unable to find it though.
In any case, understood about it being somewhat fragile/dubious in general. I’ve ended up just writing a proper wrapper.