Allow CXX and CPPFLAGS override

Makefile

@@ -1,5 +1,5 @@
-CXX=c++
-CPPFLAGS=	-Wall 				\
+CXX ?= c++
+CPPFLAGS ?=	-Wall 				\
 		-Wextra				\
 		-pipe				\
 		-Wmissing-declarations		\
@@ -9,7 +9,7 @@ CPPFLAGS=	-Wall 				\
 
 LDFLAGS=-lncursesw -Wl,-z,relro,-z,now
 
-SOURCES=main.cpp	\
+SOURCES =	main.cpp	\
 		chess.cpp	\
 		bishop.cpp	\
 		rook.cpp	\
@@ -18,8 +18,8 @@ SOURCES=main.cpp	\
 		knight.cpp	\
 		pawn.cpp
 
-OBJECTS=$(SOURCES:.cpp=.o)
-EXECUTABLE=chess
+OBJECTS = $(SOURCES:.cpp=.o)
+EXECUTABLE = chess
 
 all: $(SOURCES) $(EXECUTABLE)