message: better error msg on missing antlr4 installation
diff: @@ -17,7 +17,7 @@ else()
  set(_ANTLR_JAR_LOCATION ${_ANTLR_JAR_LOCATION_${antlr_jar}})
  MESSAGE(STATUS "using ${antlr_jar} found in ${_ANTLR_JAR_LOCATION}")
  if (NOT _ANTLR_JAR_LOCATION)
  - MESSAGE(FATAL_ERROR "Can not find ${antlr_jar}")
  + MESSAGE(FATAL_ERROR "Can not find ${antlr_jar} jar file from ANTLR installation")
  endif()
  if(ANTLR_CLASSPATH)
  set(ANTLR_CLASSPATH "${ANTLR_CLASSPATH}:${_ANTLR_JAR_LOCATION}")
  