cmake: improve check again make-based build system

  set(CMAKE_BUILD_TYPE Release CACHE STRING "Choose the type of build, options are: None Debug Release RelWithDebInfo MinSizeRel." FORCE)

endif(NOT CMAKE_BUILD_TYPE AND NOT CMAKE_CXX_FLAGS)

# remove any style headers in the src dir

file(GLOB SRC_STYLE_FILES ${LAMMPS_SOURCE_DIR}/style_*.h)

if(SRC_STYLE_FILES)

  file(REMOVE ${SRC_STYLE_FILES})

# check for files installed by make-based buildsystem 

file(GLOB SRC_STYLE_FILES ${LAMMPS_SOURCE_DIR}/*/*.cpp)

foreach(_SRC SRC_STYLE_FILES)

  get_filename_component(FILENAME "${_SRC}" NAME)

  if(EXISTS ${LAMMPS_SOURCE_DIR}/${FILENAME})

    message(FATAL_ERROR "Found packages installed by the make-based buildsystem, please run 'make -C ${LAMMPS_SOURCE_DIR} no-all purge'")

  endif()

endforeach()

enable_language(CXX)