Index: paperjam-1.1.1/Makefile
===================================================================
--- paperjam-1.1.1.orig/Makefile
+++ paperjam-1.1.1/Makefile
@@ -3,12 +3,12 @@ YEAR=2020
 BUILD_DATE:=$(shell if [ -e .git ] ; then git log -1 --format=%cs ; else date -u -r NEWS '+%Y-%m-%d' 2>/dev/null || date '+%Y-%m-%d' ; fi)
 BUILD_COMMIT:=$(shell if git rev-parse >/dev/null 2>/dev/null ; then git describe --always --tags ; else echo '<unknown>' ; fi)
 
-DESTDIR=
-PREFIX=/usr/local
-BINDIR=$(PREFIX)/bin
-MANDIR=$(PREFIX)/share/man
+DESTDIR?=
+PREFIX?=/usr/local
+BINDIR?=$(PREFIX)/bin
+MANDIR?=$(PREFIX)/share/man
 
-CXXFLAGS=-O2 -Wall -Wextra -Wno-parentheses -std=gnu++11 -g
+CXXFLAGS?=-O2 -Wall -Wextra -Wno-parentheses -g
 
 all: paperjam paperjam.1 paperjam.1.html