[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/multithread.sh

@@ -0,0 +1,45 @@
+#!/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" ] || [ -z "$hasMT" ]; then
+    # Skip tests if we have a non-deterministic build
+    cat "$CLI_TESTS/determinism/multithread.sh.stdout.exact"
+    exit 0
+fi
+
+for level in 1 3 7 19; do
+    for file in $(ls files/); do
+        file="files/$file"
+        echo "level $level, file $file"
+        zstd -T2 -q -$level $file -c | md5hash
+    done
+done
+
+for file in $(ls files/); do
+    file="files/$file"
+    echo "level 1, long=18, file $file"
+    zstd --long=18 -T2 -q -1 $file -c | md5hash
+    echo "level 19, long=18, file $file"
+    zstd --long=18 -T2 -q -19 $file -c | md5hash
+done
+
+for file in $(ls files/); do
+    file="files/$file"
+    echo "Vary number of threads on $file"
+    zstd -qf -1 $file -o $file.zst.good
+
+    zstd -qf -T1 -1 $file
+    $DIFF $file.zst $file.zst.good
+
+    zstd -qf -T2 -1 $file
+    $DIFF $file.zst $file.zst.good
+
+    zstd -qf -T4 -1 $file
+    $DIFF $file.zst $file.zst.good
+done