lang/rust*: Bring back the llvm-config-wrapper patches after r543251

Apparently they are still needed:
http://gohan03.nyi.freebsd.org/data/head-amd64-default-baseline/p543836_s363720/logs/errors/rust-1.45.1.log
http://gohan03.nyi.freebsd.org/data/head-amd64-default-baseline/p543836_s363720/logs/errors/rust-nightly-1.47.0.20200724.log
http://gohan03.nyi.freebsd.org/data/head-amd64-default-baseline/p544005_s363784/logs/errors/rust-1.45.1.log

Reported by: antoine