test-periodic: build with same C++ compiler as ROOT

If not built with the same compiler, CMAKE_CXX_FLAGS may contain
flags not known by the default compiler, which will make the test
fail. In particular using Ninja + Clang on Linux makes this test
fail with the error below without this patch.

c++: error: unrecognized command line option ‘-fcolor-diagnostics’
ninja: build stopped: subcommand failed.

test/CMakeLists.txt

@@ -367,7 +367,10 @@ if (NOT cxxmodules)
   # the current test will not require the VecCore (as in the textual case).
   # Alternatively, we can trace the origin of the fatal error and try to remap
   # the source locations.
-  ROOT_ADD_TEST(test-periodic-build COMMAND ${CMAKE_CTEST_COMMAND}
-                                    --build-and-test ${CMAKE_CURRENT_SOURCE_DIR}/periodic periodic-build
-                                    --build-generator ${CMAKE_GENERATOR})
+  ROOT_ADD_TEST(test-periodic-build
+    COMMAND
+      env CC=${CMAKE_C_COMPILER} CXX=${CMAKE_CXX_COMPILER}
+      ${CMAKE_CTEST_COMMAND} --build-generator ${CMAKE_GENERATOR}
+      --build-and-test ${CMAKE_CURRENT_SOURCE_DIR}/periodic periodic-build
+  )
 endif()