Default install target to use /usr/local prefix

While also allowing to customise PREFIX and DESTDIR

Makefile

@@ -3,6 +3,10 @@ CFLAGS+= -g -O2 -Wall -Wextra -lgumbo -lcurl -lfuse -lcrypto \
 	-D_FILE_OFFSET_BITS=64
 OBJ = main.o network.o fuse_local.o link.o
 
+PREFIX ?= /usr/local
+INSTALL = /usr/bin/install
+INSTALL_OPTS = -m 0755
+
 %.o: %.c
 	$(CC) -c -o $@ $< $(CPPFLAGS) $(CFLAGS) $(LDFLAGS)
 
@@ -10,7 +14,8 @@ httpdirfs: $(OBJ)
 	$(CC) -o $@ $^ $(CPPFLAGS) $(CFLAGS) $(LDFLAGS)
 
 install:
-	cp httpdirfs ${HOME}/bin/
+	mkdir -p $(DESTDIR)$(PREFIX)/bin
+	$(INSTALL) $(INSTALL_OPTS) httpdirfs $(DESTDIR)$(PREFIX)/bin
 
 doc:
 	doxygen Doxyfile