pass the installation prefix of libffi to ECL

[dimpase]

at present ECL installation takes the headers of libffi from whereever it can, and first of all from "standard" locations. Thus an imcompatible libffi headers (and version 3.3 introduced an apparent incompatibility) installed system-wide break building of ECL even though --without-system-ecl is given.

This was reported to happen on Debian testing.
(And an earlier related ticket is #21811). The initial debugging started on this thread of sage-devel.

ECL's configure has an option --with-libffi-prefix=path which hopefully does the job (untested); if so, this would at least allow
the build to succeed in such a configuration.

Another task is to test for the incompatible libffi (well, we can just test the version not to be above 3.2.x for some x).

CC: @mkoeppe @isuruf @embray @kiwifb @EmmanuelCharpentier @mezzarobba

Component: build

Reviewer: Travis Scrimshaw

Issue created by migration from https://trac.sagemath.org/ticket/29128

[dimpase]

comment:4

In upstream ECL it's addressed in https://gitlab.com/embeddable-common-lisp/ecl/issues/302

So we hopefully can backport this to out 16.1.2, and support all versions of libffi, old and current.

[dimpase]

comment:5

the ECL's option appears not be working, anyway, on #21811 there is a better solution.
We'll fix the issue on #21811

[tscrim]

Reviewer: Travis Scrimshaw

[tscrim]

comment:6

Since #21811 is a better solution and positively reviewed, I agree with closing this.