message: fix cmake option USE_POSTFIX
  appending the suffix to the build product need not be a function of
  whether CMAKE_CONFIGURATION_TYPES is set.  for example, having two ninja
  build trees---one for debug and another for release---is a fine use-case
  for USE_POSTFIX.
diff: @@ -81,7 +81,7 @@ foreach(TARGET ${LIBRARY})
  $<BUILD_INTERFACE:${CMAKE_CURRENT_LIST_DIR}/src>
  $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}${INSTALL_SUFFIX}>)
  - if(USE_POSTFIX AND CMAKE_CONFIGURATION_TYPES)
  + if(USE_POSTFIX)
  set_target_properties(${TARGET} PROPERTIES DEBUG_POSTFIX "_d" MINSIZEREL_POSTFIX "_m" RELWITHDEBINFO_POSTFIX "_r")
  endif()
  endforeach()
  