Merge #14937: travis: fix travis would always be green even if it fail

fc91c1f Revert "travis: Save cache on build error" (Chun Kuan Lee)

Pull request description:

  The current travis-ci job would fail only if the last command failed. It would be succeed if other commands than the last one fail.

  This PR execute the script in another shell instance, so we should export those variables and bash functions. It would return 1 if the script fail no matter if it's the last command.

  Sorry for ruin the travis ci system in #14231

  Test: https://travis-ci.org/ken2812221/bitcoin/jobs/467086010

Tree-SHA512: 4d9d144fe4c7038b4eff6bf8496e821af603d81677142c0884ed52aea6ce3a50150669be4fdad72a5d372456a33a2452d75ec35e8a7ec2bc4bdfbeaeb93e9acb

Author: MarcoFalke

.travis.yml

@@ -26,13 +26,13 @@ env:
     - WINEDEBUG=fixme-all
     - DOCKER_PACKAGES="build-essential libtool autotools-dev automake pkg-config bsdmainutils curl git ca-certificates ccache"
 before_install:
-  - set -o errexit; if ! source .travis/test_03_before_install.sh; then set +o errexit; false; fi
+  - set -o errexit; source .travis/test_03_before_install.sh
 install:
-  - set -o errexit; if ! source .travis/test_04_install.sh; then set +o errexit; false; fi
+  - set -o errexit; source .travis/test_04_install.sh
 before_script:
-  - set -o errexit; if ! source .travis/test_05_before_script.sh; then set +o errexit; false; fi
+  - set -o errexit; source .travis/test_05_before_script.sh
 script:
-  - if [ $SECONDS -gt 1200 ]; then set +o errexit; echo "Travis early exit to cache current state"; false; else set -o errexit; if ! source .travis/test_06_script.sh; then set +o errexit; false; fi; fi
+  - if [ $SECONDS -gt 1200 ]; then set +o errexit; echo "Travis early exit to cache current state"; false; else set -o errexit; source .travis/test_06_script.sh; fi
 after_script:
   - echo $TRAVIS_COMMIT_RANGE
   - echo $TRAVIS_COMMIT_LOG