message: Fix Makefile bash command for POSIX conformance
  This fixes errors seen when compiling on Ubuntu Linux.
diff: @@ -21,7 +21,7 @@ ${TARGET}: ${OBJ} ./API/NAS2D/lib/libnas2d.a
  ${DIR_OBJ}/%.o: ${DIR_SRC}/%.cpp ${INC_H}# ${INC_CPP}
  @mkdir -p ${@D}
  @dirs=$(dir $<); \
  - if [ "$${dirs#*ui_builder/}" == "$$dirs" ]; \
  + if [ "$${dirs#*ui_builder/}" = "$$dirs" ]; \
  then ${CXX} -c $< ${CFLAGS} -o $@; \
  fi
  