Remove redundant CMake flag -DCMAKE_CXX_FLAGS=-Wno-error=switch-enum

.adjustments made to simplify libenvpp configuration in CMake.

Author: allnes

cmake/libenvpp.cmake

@@ -9,6 +9,6 @@ ExternalProject_Add(ppc_libenvpp
         INSTALL_DIR       "${CMAKE_CURRENT_BINARY_DIR}/ppc_libenvpp/install"
         CONFIGURE_COMMAND "${CMAKE_COMMAND}" -S "${CMAKE_SOURCE_DIR}/3rdparty/libenvpp/" -B "${CMAKE_CURRENT_BINARY_DIR}/ppc_libenvpp/build/"
         -DCMAKE_CXX_COMPILER=${CMAKE_CXX_COMPILER} -G${CMAKE_GENERATOR} -DCMAKE_BUILD_TYPE=${CMAKE_BUILD_TYPE}
-        -D CMAKE_C_COMPILER_LAUNCHER=${CMAKE_C_COMPILER_LAUNCHER} -D CMAKE_CXX_COMPILER_LAUNCHER=${CMAKE_CXX_COMPILER_LAUNCHER} -DCMAKE_CXX_FLAGS=-Wno-error=switch-enum
+        -D CMAKE_C_COMPILER_LAUNCHER=${CMAKE_C_COMPILER_LAUNCHER} -D CMAKE_CXX_COMPILER_LAUNCHER=${CMAKE_CXX_COMPILER_LAUNCHER}
         BUILD_COMMAND     "${CMAKE_COMMAND}" --build "${CMAKE_CURRENT_BINARY_DIR}/ppc_libenvpp/build" --config ${CMAKE_BUILD_TYPE} --parallel
         INSTALL_COMMAND   "${CMAKE_COMMAND}" --install "${CMAKE_CURRENT_BINARY_DIR}/ppc_libenvpp/build" --prefix "${CMAKE_CURRENT_BINARY_DIR}/ppc_libenvpp/install")