Merge #16367: Multiprocess build support

b919efadff depends: Use default macos clang compiler (Russell Yanofsky)
d54f64c6c7 Add multiprocess travis configuration (Russell Yanofsky)
787f40668d Set LD_LIBRARY_PATH consistently in travis tests (Russell Yanofsky)
d630646662 libmultiprocess depends build (Russell Yanofsky)
e6e44eedd5 Multiprocess build changes (Russell Yanofsky)

Pull request description:

  This PR is part of the [process separation project](https://github.com/bitcoin/bitcoin/projects/10).

  This splits autotools, depends build, and travis changes out of #10102, so code changes and build system changes can be reviewed separately.

ACKs for top commit:
  hebasto:
    re-ACK b919efadff, rebased only since my [previous](https://github.com/bitcoin/bitcoin/pull/16367#issuecomment-605514556) review.

Tree-SHA512: ebc5e403cc99a0d9629ed7fe1595e01d57e6d1255cbf03968a3196ff6f528f734c78060fdc065724ee1f923bcc5aa2b29470fcb36a7f15957eb57c76d58178a4

ci/test/00_setup_env_native_multiprocess.sh

@@ -0,0 +1,14 @@
+#!/usr/bin/env bash
+#
+# Copyright (c) 2020 The Bitcoin Core developers
+# Distributed under the MIT software license, see the accompanying
+# file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+export LC_ALL=C.UTF-8
+
+export CONTAINER_NAME=ci_native_multiprocess
+export PACKAGES="cmake python3"
+export DEP_OPTS="MULTIPROCESS=1"
+export GOAL="install"
+export BITCOIN_CONFIG=""
+export TEST_RUNNER_ENV="BITCOIND=bitcoin-node"

ci/test/06_script_b.sh

@@ -37,12 +37,12 @@ fi
 
 if [ "$RUN_FUNCTIONAL_TESTS" = "true" ]; then
   BEGIN_FOLD functional-tests
-  DOCKER_EXEC test/functional/test_runner.py --ci $MAKEJOBS --tmpdirprefix "${BASE_SCRATCH_DIR}/test_runner/" --ansi --combinedlogslen=4000 ${TEST_RUNNER_EXTRA} --quiet --failfast
+  DOCKER_EXEC LD_LIBRARY_PATH=$DEPENDS_DIR/$HOST/lib ${TEST_RUNNER_ENV} test/functional/test_runner.py --ci $MAKEJOBS --tmpdirprefix "${BASE_SCRATCH_DIR}/test_runner/" --ansi --combinedlogslen=4000 ${TEST_RUNNER_EXTRA} --quiet --failfast
   END_FOLD
 fi
 
 if [ "$RUN_FUZZ_TESTS" = "true" ]; then
   BEGIN_FOLD fuzz-tests
-  DOCKER_EXEC test/fuzz/test_runner.py ${FUZZ_TESTS_CONFIG} -l DEBUG ${DIR_FUZZ_IN}
+  DOCKER_EXEC LD_LIBRARY_PATH=$DEPENDS_DIR/$HOST/lib test/fuzz/test_runner.py ${FUZZ_TESTS_CONFIG} -l DEBUG ${DIR_FUZZ_IN}
   END_FOLD
 fi