Merge #17900: ci: Combine 32-bit build with CentOS 7 build

ef63f5f ci: Combine 32-bit build with CentOS 7 build (Sebastian Falbesoner)

Pull request description:

  Combines the CentOS build with the 32-bit (i686) build to avoid Travis bottlenecks, as suggested in #17757 by MarcoFalke. This keeps most of the properties of the 32-bit build (dash as config shell, building QT5 GUI) and just builds it with depends inside the CentOS docker container.

  Making the depends in `05_before_script.sh` with unset config shell (`CONFIG_SHELL=`)

  https://github.com/bitcoin/bitcoin/blob/6196e930018181301b5972842ae384ea4288ff34/ci/test/05_before_script.sh#L28

  caused problems for building the library libevent (resulting in a Makefile with no shell set (`SHELL=`)), that's why I set it explicitely to `/bin/bash` if we have a CentOS Docker container.

  A Travis output of this 32-bit CentOS build can be seen here: https://travis-ci.org/theStack/bitcoin/jobs/634472394 (has been restarted once due to too long build time and appearance of the `CACHE_ERR_MSG`).

  For anyone wanting to verify the outputs, I found these instructions useful to reproduce a Travis build locally: https://github.com/erdc/proteus/wiki/Replicating-the-TravisCI-Environment-on-your-Local-Machine (steps 1-3). In this case it's a bit tricky since you run Docker inside Docker -- within the Travis Docker container, the CentOS Docker container is created. To make this possible, the Docker socket has to be exposed to the Travis container via bind-mounting (`docker run -v /var/run/docker.sock:/var/run/docker.sock ...`), as suggested in https://stackoverflow.com/a/33003273.

Top commit has no ACKs.

Tree-SHA512: af508241cec3a10a66c37673d56691717b78375340e910fcdd3fb3870741eba623a436e1e85b26b54f013375611896f5411c5a7fec2437d367d27172230129fe

Author: MarcoFalke

.travis.yml

@@ -101,14 +101,9 @@ jobs:
         FILE_ENV="./ci/test/00_setup_env_win64.sh"
 
     - stage: test
-      name: '32-bit + dash  [GOAL: install]  [gui]'
+      name: '32-bit + dash  [GOAL: install]  [CentOS 7]  [gui]'
       env: >-
-        FILE_ENV="./ci/test/00_setup_env_i686.sh"
-
-    - stage: test
-      name: 'x86_64 Linux  [GOAL: install]  [CentOS 7]  [no depends, only system libs]'
-      env: >-
-        FILE_ENV="./ci/test/00_setup_env_native_centos.sh"
+        FILE_ENV="./ci/test/00_setup_env_i686_centos.sh"
 
     - stage: test
       name: 'x86_64 Linux  [GOAL: install]  [bionic]  [uses qt5 dev package and some depends packages] [unsigned char]'

ci/test/00_setup_env_i686.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 HOST=i686-pc-linux-gnu
+export DOCKER_NAME_TAG=centos:7
+export DOCKER_PACKAGES="gcc-c++ glibc-devel.x86_64 libstdc++-devel.x86_64 glibc-devel.i686 libstdc++-devel.i686 ccache libtool make git python3 python36-zmq which patch lbzip2 dash"
+export GOAL="install"
+export BITCOIN_CONFIG="--enable-zmq --with-gui=qt5 --enable-reduce-exports"
+export CONFIG_SHELL="/bin/dash"

ci/test/00_setup_env_i686_centos.sh

@@ -25,5 +25,13 @@ if [[ $HOST = *-mingw32 ]]; then
   DOCKER_EXEC update-alternatives --set $HOST-g++ \$\(which $HOST-g++-posix\)
 fi
 if [ -z "$NO_DEPENDS" ]; then
-  DOCKER_EXEC CONFIG_SHELL= make $MAKEJOBS -C depends HOST=$HOST $DEP_OPTS
+  if [[ $DOCKER_NAME_TAG == centos* ]]; then
+    # CentOS has problems building the depends if the config shell is not explicitely set
+    # (i.e. for libevent a Makefile with an empty SHELL variable is generated, leading to
+    #  an error as the first command is executed)
+    SHELL_OPTS="CONFIG_SHELL=/bin/bash"
+  else
+    SHELL_OPTS="CONFIG_SHELL="
+  fi
+  DOCKER_EXEC $SHELL_OPTS make $MAKEJOBS -C depends HOST=$HOST $DEP_OPTS
 fi