add option to delete files that are not "compressed" #302

Job	Run time
Build and test cmake:gcc9	48s
Build and test cmake:clang12	55s
Build and test cmake:clang12:asan	1m 16s
Build and test cmake:clang12:tsan	1m 18s
Build and test cmake:clang12:ubsan	1m 9s
Build and test cmake:qemu-arm-neon-gcc	2m 35s
Build and test cmake-osx:clang	2m 59s
Build and test cmake-osx:gcc	51s
Build and test cmake-win64:msvc2019-rel	1m 40s
Build and test cmake-win64:msvc2019-dbg	50s
Build and test fuzz:clang12	39s
Build and test python39:clang12	2m 14s
Build and test python39-win	52s
Build and test maven	56s
Build and test bazel:root	46s
Build and test bazel:go	54s
Build and test bazel:java	3m 21s
Build and test bazel:js	5m 22s
Build and test bazel:research	32s
Build and test bazel-osx:root	2m 51s
Build and test bazel-osx:go	4m 11s
Build and test bazel-osx:java	4m 41s
Build and test bazel-osx:js	8m 23s
Build and test bazel-osx:research	6m 18s
Build and test bazel-win:root	1m 17s
Build and test bazel-win:java	5m 58s
Build and test bazel-win:research	53s
	1h 4m 29s

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