--- afio-2.5.1/Makefile.orig	2012-02-05 08:52:24.000000000 -0500
+++ afio-2.5.1/Makefile	2016-08-24 12:54:43.673031190 -0400
@@ -1,4 +1,8 @@
-SHELL=/bin/sh
+DESTDIR?=
+PREFIX?=/usr/local
+BINDIR?=$(PREFIX)/bin
+MANDIR?=/usr/share/man
+SHELL?=/bin/sh
 ##
 ##  See the INSTALLATION file for quick installation instructions.
 ##
@@ -73,10 +77,11 @@ MW=
 
 CFLAGS1 = -Wall -Wstrict-prototypes -s -O2 -fomit-frame-pointer ${LARGEFILEFLAGS} ${MW}
 
-CC=gcc
+CC?=gcc
 
-CFLAGS = ${CFLAGS1} $1 $2 $3 $4 $5 $6 $7 $8 $9 $a $b $c $d $e ${e2} $f $g $I
-LDFLAGS =
+CFLAGS ?= ${CFLAGS1}
+CFLAGS += $1 $2 $3 $4 $5 $6 $7 $8 $9 $a $b $c $d $e ${e2} $f $g $I
+LDFLAGS ?=
 
 afio : afio.o compfile.o exten.o match.o $M
 	${CC} ${LDFLAGS} afio.o compfile.o exten.o match.o $M -o afio
@@ -88,8 +93,10 @@ clean:
 	cd regtest; /bin/sh regtest.clean
 
 install: afio
-	cp afio /usr/local/bin
-	cp afio.1 /usr/share/man/man1
+	mkdir -p $(DESTDIR)$(BINDIR)
+	mkdir -p $(DESTDIR)$(MANDIR)/man1
+	cp afio $(DESTDIR)$(BINDIR)
+	cp afio.1 $(DESTDIR)$(MANDIR)/man1
 
 # generate default list of -E extensions from manpage
 # note: on sun, I had to change awk command below to nawk or gawk