Created attachment 3781 [details]
diffoscope output of two bzip2-ptest debian packages

bzip2-ptest requires Makefile. This file contains numerous references to the host build system (see the attached diffoscope output). These are harmless and also unneeded, as the ptest runs this:

$ make -k runtest

and the "runtest" target in the Makefile is:

runtest:
	./bzip2 -1  < sample1.ref > sample1.rb2
	./bzip2 -2  < sample2.ref > sample2.rb2
	./bzip2 -3  < sample3.ref > sample3.rb2
	./bzip2 -d  < sample1.bz2 > sample1.tst
	./bzip2 -d  < sample2.bz2 > sample2.tst
	./bzip2 -ds < sample3.bz2 > sample3.tst
	@if cmp sample1.bz2 sample1.rb2; then echo "PASS: sample1 compress";\
	else echo "FAIL: sample1 compress"; fi
	@if cmp sample2.bz2 sample2.rb2; then echo "PASS: sample2 compress";\
	else echo "FAIL: sample2 compress"; fi
	@if cmp sample3.bz2 sample3.rb2; then echo "PASS: sample3 compress";\
	else echo "FAIL: sample3 compress"; fi
	@if cmp sample1.tst sample1.ref; then echo "PASS: sample1 decompress";\
	else echo "FAIL: sample1 decompress"; fi
	@if cmp sample2.tst sample2.ref; then echo "PASS: sample2 decompress";\
	else echo "FAIL: sample2 decompress"; fi
	@if cmp sample3.tst sample3.ref; then echo "PASS: sample3 decompress";\
	else echo "FAIL: sample3 decompress"; fi


The references to the host build system prevent the bzip2-ptest package from being binary reproducible.
One option is to sanitize all host references, the other (probably better) is to create/install only the relevant part of the Makefile