Add required variables for cibuildwheel on Travis

Co-authored by: nijincheng@iscas.ac.cn;

Author: ffgan

.travis.yml

@@ -38,10 +38,18 @@ install:
     # Maybe get and clean and patch source
     - |
       python3 -m pip install cibuildwheel==3.2.1
+      python3 -m cibuildwheel --help # make sure it is installed correctly
       echo done install step
 
 script:
-    - python3 -m cibuildwheel --output-dir dist
+    - |
+      export CIBW_BUILD="cp39-manylinux_${PLAT}"
+      export CIBW_MANYLINUX_S390X_IMAGE="manylinux${MB_ML_VER}"
+      export CIBW_MANYLINUX_PPC64LE_IMAGE="manylinux${MB_ML_VER}"
+
+      python3 -m cibuildwheel --print-build-identifiers
+
+      python3 -m cibuildwheel --output-dir dist
 
 after_success:
     - set +ex