--- a/Makefile
+++ b/Makefile
@@ -5,9 +5,10 @@
 
 PACKAGE = genromfs
 VERSION = 0.5.7
-CC = gcc
-CFLAGS = -O2 -Wall -DVERSION=\"$(VERSION)\"#-g#
-LDFLAGS = -s#-g
+CC ?= gcc
+CFLAGS ?= -O2
+CFLAGS += -Wall -DVERSION=\"$(VERSION)\"#-g#
+LDFLAGS ?= -s#-g
 
 DISTDIR = $(PACKAGE)-$(VERSION)
 
@@ -17,9 +18,9 @@
  checkdist \
  .gitignore selftest
 
-prefix = /usr
+prefix = $(DESTDIR)/usr
 bindir = $(prefix)/bin
-mandir = $(prefix)/man
+mandir = $(prefix)/share/man
 
 genromfs: genromfs.o
 	$(CC) $(LDFLAGS) genromfs.o -o genromfs