[test] Add tests for determinism

Run compression & validate the compressed file matches a known checksum.

To update the output run:

```
make -C tests update-cli-tests
```

tests/cli-tests/determinism/reuse.sh

@@ -0,0 +1,44 @@
+#!/bin/sh
+
+. "$COMMON/platform.sh"
+
+set -e
+
+# To update checksums on version change run this from the tests/ directory
+# make update-cli-tests
+
+if [ -n "$NON_DETERMINISTIC" ]; then
+    # Skip tests if we have a non-deterministic build
+    cat "$CLI_TESTS/determinism/reuse.sh.stdout.exact"
+    exit 0
+fi
+
+datagen -g0 > file0
+datagen -g1 > file1
+datagen -g1000 > file1000
+datagen -g100000 > file100000
+
+validate() {
+    $DIFF file0.zst file0.zst.good
+    $DIFF file1.zst file1.zst.good
+    $DIFF file1000.zst file1000.zst.good
+    $DIFF file100000.zst file100000.zst.good
+}
+
+# Check that context reuse doesn't impact determinism
+for level in $(seq 1 19); do
+    echo $level
+    zstd -qf --single-thread -$level file0 -o file0.zst.good
+    zstd -qf --single-thread -$level file1 -o file1.zst.good
+    zstd -qf --single-thread -$level file1000 -o file1000.zst.good
+    zstd -qf --single-thread -$level file100000 -o file100000.zst.good
+
+    zstd -qf --single-thread -$level file0 file1 file1000 file100000
+    validate
+    zstd -qf --single-thread -$level file1 file0 file1000 file100000
+    validate
+    zstd -qf --single-thread -$level file1000 file1 file0 file100000
+    validate
+    zstd -qf --single-thread -$level file100000 file1000 file1 file0
+    validate
+done