Enabled flat namespace in macOS travis builds.

Author: STCE2023

.travis.yml

@@ -29,7 +29,9 @@ matrix:
   - os: osx
     name: "CMake Release Test on macOS Big Sur"
     osx_image: xcode12.3
-    env: CMAKE_BUILD_TYPE=Release
+    env:
+      - CMAKE_BUILD_TYPE=Release
+      - ADDITIONAL_CMAKE_OPTIONS="-DUSE_FLAT_NAMESPACE:BOOL=ON"
   - os: osx
     osx_image: xcode12.3
     name: "Makefile Test on on macOS Big Sur"
@@ -62,6 +64,7 @@ script:
     -DBUILD_SHARED_LIBS:BOOL=ON
     -DCMAKE_Fortran_FLAGS:STRING="-fimplicit-none -frecursive -fcheck=all"
     -DCMAKE_C_FLAGS=${CMAKE_C_FLAGS}
+    ${ADDITIONAL_CMAKE_OPTIONS}
     ${SRC_DIR}
   - ctest -D ExperimentalStart
   - ctest -D ExperimentalConfigure