list(REMOVE_ITEM support_sources
${TOP_SRC_DIR}/src/support/os_win32.cpp
${TOP_SRC_DIR}/src/support/os_unix.cpp
${TOP_SRC_DIR}/src/support/os_cygwin.cpp
${TOP_SRC_DIR}/src/support/os_os2.C
list(REMOVE_ITEM support_sources
${TOP_SRC_DIR}/src/support/os_win32.cpp
${TOP_SRC_DIR}/src/support/os_unix.cpp
${TOP_SRC_DIR}/src/support/os_cygwin.cpp
${TOP_SRC_DIR}/src/support/os_os2.C