[SECP256K1] build: Add workaround for automake 1.13 and older

Summary: Backport of secp256k1#891

Test Plan: Build with autotools (I did not check the old automake version).

Reviewers: #bitcoin_abc, PiRK

Reviewed By: #bitcoin_abc, PiRK

Differential Revision: https://reviews.bitcoinabc.org/D9390