[ci] use boost::process

Explictly opt-out on win64, in case the default changes.

ci/test/00_setup_env_native_fuzz.sh

@@ -14,5 +14,5 @@ export RUN_UNIT_TESTS=false
 export RUN_FUNCTIONAL_TESTS=false
 export RUN_FUZZ_TESTS=true
 export GOAL="install"
-export BITCOIN_CONFIG="--enable-fuzz --with-sanitizers=fuzzer,address,undefined CC=clang CXX=clang++"
+export BITCOIN_CONFIG="--enable-fuzz --with-sanitizers=fuzzer,address,undefined CC=clang CXX=clang++ --with-boost-process"
 export CCACHE_SIZE=200M