- fixed CI/CD error "unmappable character for encoding"

Makefile

@@ -79,7 +79,7 @@ $(JAR): $(OBJS)
 	@cd $(BUILD); ${JAVAPATH}/jar cfvM ../$@ ./* ; cd ..
 
 %.class: %.java
-	${JAVAPATH}/javac --release ${JAVARELEASE} -g -classpath ${CLASSPATH}:${JUNITCLASSPATH} -Xlint:all $<
+	${JAVAPATH}/javac -encoding utf-8 --release ${JAVARELEASE} -g -classpath ${CLASSPATH}:${JUNITCLASSPATH} -Xlint:all $<
 
 doc: $(SOURCES)
 	javadoc -d doc/ $^