fix dependency lcg.h in CMakeLists and Makefile.test.include

Summary:
was causing failed gitian

(my bad, was introduced in D2480)

Test Plan: Jason ran the gitian build on this patch successfully.

Reviewers: #bitcoin_abc, deadalnix, jasonbcox

Reviewed By: #bitcoin_abc, jasonbcox

Subscribers: teamcity, schancel

Differential Revision: https://reviews.bitcoinabc.org/D2489