ci: Add ppc64le and s390x tests to TravisCI

We removed these tests because of our broken interface. Now, we aim to
fix this issue and thus, expect it to work again.

Signed-off-by: Johannes Demel <[email protected]>

Author: jdemel

.travis.yml

@@ -56,6 +56,16 @@ matrix:
       env: MATRIX_EVAL="CC=clang && CXX=clang++"
       addons: {apt: {packages: [*common_packages, ]}}
 
+    - name: Linux s390x GCC 7
+      arch: s390x
+      env: MATRIX_EVAL="CC=gcc-7 && CXX=g++-7"
+      addons: {apt: {packages: [*common_packages, ]}}
+
+    - name: Linux ppc64le GCC 7
+      arch: ppc64le
+      env: MATRIX_EVAL="CC=gcc-7 && CXX=g++-7"
+      addons: {apt: {packages: [*common_packages, ]}}
+      
 script:
   - eval "${MATRIX_EVAL}"
   - lscpu