Travis CI: Try to determine environment variables for debugging the build

.travis.yml

@@ -2707,15 +2707,15 @@ install:
 
 before_script:
   # Check some settings of the build server
-  - echo "Commit Id: ${TRAVIS_COMMIT}"
-  - echo "Commit Tag: ${TRAVIS_TAG}"
-  - echo "Repo: ${TRAVIS_REPO_SLUG}"
-  - echo "Branch: ${TRAVIS_BRANCH}"
-  - echo "Job: ${TRAVIS_JOB_NUMBER}"
-  - echo "OS: ${TRAVIS_OS_NAME}"
-  - echo "Compiler: ${CC}"
-  - echo "Features: ${FEATURES}"
-  - echo "Reference configuration: ${REFERENCE_BUILD}"
+  - bash -c echo "Commit Id: ${TRAVIS_COMMIT}"
+  - bash -c echo "Commit Tag: ${TRAVIS_TAG}"
+  - bash -c echo "Repo: ${TRAVIS_REPO_SLUG}"
+  - bash -c echo "Branch: ${TRAVIS_BRANCH}"
+  - bash -c echo "Job: ${TRAVIS_JOB_NUMBER}"
+  - bash -c echo "OS: ${TRAVIS_OS_NAME}"
+  - bash -c echo "Compiler: ${CC}"
+  - bash -c echo "Features: ${FEATURES}"
+  - bash -c echo "Reference configuration: ${REFERENCE_BUILD}"
   - uname -a
   - pwd
   # Generate the build scripts with CMake