build: dont compile rapidcheck with -Wall

Summary:
This fixes the depends build with GCC 9.1.

Backport of core PR16271.

Depends on D5324.

Test Plan:
Assuming you are running a 64-bit Linux machine:

cd depends
RAPIDCHECK=1 make build-linux64

Check the rapidcheck package is built.

cd .. && mkdir buildLinux64 && cd buildLinux64
cmake -GNinja .. \
  -DCMAKE_TOOLCHAIN_FILE=../cmake/platforms/Linux64.cmake \
  -DENABLE_PROPERTY_BASED_TESTS=ON

Check the rapidcheck lib found is the one from the depends.

ninja check

Reviewers: #bitcoin_abc, jasonbcox

Reviewed By: #bitcoin_abc, jasonbcox

Differential Revision: https://reviews.bitcoinabc.org/D5325