[test] Add new CLI testing platform

Adds the new CLI testing platform that I'm proposing.
See the added `README.md` for details.

tests/cli-tests/bin/cmp_size

@@ -0,0 +1,46 @@
+#!/bin/sh
+
+# Small utility to
+
+set -e
+
+usage()
+{
+	printf "USAGE:\n\t$0 [-eq|-ne|-lt|-le|-gt|-ge] FILE1 FILE2\n"
+}
+
+help()
+{
+	printf "Small utility to compare file sizes without printing them with set -x.\n\n"
+	usage
+}
+
+case "$1" in
+	-h) help; exit 0  ;;
+	--help) help; exit 0 ;;
+esac
+
+if ! test -f $2; then
+	printf "FILE1='%b' is not a file\n\n" "$2"
+	usage
+	exit 1
+fi
+
+if ! test -f $3; then
+	printf "FILE2='%b' is not a file\n\n" "$3"
+	usage
+	exit 1
+fi
+
+
+size1=$(wc -c < $2)
+size2=$(wc -c < $3)
+
+case "$1" in
+	-eq) [ "$size1" -eq "$size2" ] ;;
+	-ne) [ "$size1" -ne "$size2" ] ;;
+	-lt) [ "$size1" -lt "$size2" ] ;;
+	-le) [ "$size1" -le "$size2" ] ;;
+	-gt) [ "$size1" -gt "$size2" ] ;;
+	-ge) [ "$size1" -ge "$size2" ] ;;
+esac

tests/cli-tests/bin/datagen

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+#!/bin/sh
+
+"$DATAGEN_BIN" $@

tests/cli-tests/bin/die

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+#!/bin/sh
+
+println "${*}" 1>&2
+exit 1

tests/cli-tests/bin/println

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+#!/bin/env sh
+printf '%b\n' "${*}"

tests/cli-tests/bin/unzstd

@@ -0,0 +1 @@
+zstd

tests/cli-tests/bin/zstd

@@ -0,0 +1,7 @@
+#!/bin/sh
+
+if [ -z "$EXEC_PREFIX" ]; then
+    "$ZSTD_BIN" $@
+else
+    $EXEC_PREFIX "$ZSTD_BIN" $@
+fi

tests/cli-tests/bin/zstdcat

@@ -0,0 +1 @@
+zstd

tests/cli-tests/bin/zstdgrep

@@ -0,0 +1,2 @@
+#!/bin/sh
+"$ZSTDGREP_BIN" $@