fix(makefile): -std=c++23, rm -rf ${DIR}/*

Makefile

@@ -22,7 +22,7 @@ TESTS =\
 ifeq (${origin CC}, default)
 CC = g++
 endif
-CFLAGS = -Wall -Wextra -Werror -Wno-unused-result -fPIC
+CFLAGS = -std=c++23 -Wall -Wextra -Werror -Wno-unused-result -fPIC
 ifneq (${DEBUG}, false)
 CFLAGS += -fsanitize=address,undefined -g -O0
 -g = -g
@@ -57,7 +57,7 @@ uninstall:
 	rm -f ${patsubst %, ${USRDIR}/${BINDIR}/btc-%${-g}, ${TOOLS}}
 
 clean:
-	rm -rf ${OBJDIR} ${LIBDIR} ${BINDIR}
+	rm -rf ${OBJDIR}/* ${LIBDIR}/* ${BINDIR}/*
 
 ifneq (${OBJS},)