Merge bitcoin#14231: travis: Save cache even when build or test fail

d3ecc3d travis: Save cache on build error (Chun Kuan Lee)

Pull request description:

  In current travis setup, the job will terminate immediately if an error occur. There is no chance to save the cache. This was accidentally introduced by bitcoin#13863. This PR is to fix the issue and travis would save cache on error.

  test for build error: https://travis-ci.org/bitcoin/bitcoin/builds/429172128

Tree-SHA512: fb8beb97928e10932c695d1884948bf8972a6501042d5212111fba1f258160d813a4c6cc72e9da78f2acd9518382c21943347b820d8e15b5eb874e7707c928b2

.travis.yml

@@ -70,13 +70,13 @@ builddocker: &builddocker
     - WINEDEBUG=fixme-all
     - DOCKER_PACKAGES="build-essential libtool autotools-dev automake pkg-config bsdmainutils curl git ca-certificates ccache"
 before_install:
-  - set -o errexit; source .travis/test_03_before_install.sh
+  - set -o errexit; if ! source .travis/test_03_before_install.sh; then set +o errexit; false; fi
 install:
-  - set -o errexit; source .travis/test_04_install.sh
+  - set -o errexit; if ! source .travis/test_04_install.sh; then set +o errexit; false; fi
 before_script:
-  - set -o errexit; source .travis/test_05_before_script.sh
+  - set -o errexit; if ! source .travis/test_05_before_script.sh; then set +o errexit; false; fi
 script:
-  - 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
+  - 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
 after_script:
   - echo $TRAVIS_COMMIT_RANGE
   - echo $TRAVIS_COMMIT_LOG