Build: Add a shade-check.sh to tracting-opentelemtry

Motivation
----------
Like core-io, this module shades a pre-built dependency
library, and we want to make sure the output JAR
does not contain unshaded third-party classes.

Change-Id: If966c545d9f6458dfb11d1320044a9ffa6219b86
Reviewed-on: https://review.couchbase.org/c/couchbase-jvm-clients/+/202523
Reviewed-by: David Nault <david.nault@couchbase.com>
Tested-by: David Nault <david.nault@couchbase.com>

tracing-opentelemetry/shade-check.sh

@@ -0,0 +1,46 @@
+#!/bin/sh
+
+# USAGE: Run this script from the `tracing-opentelemetry` directory after the JAR is built.
+#
+# The script exits with a non-zero status code if the tracing-opentelemetry JAR
+# contains files from a library that was not shaded correctly.
+
+set -e
+
+# Find the JAR without a "sources" or "javadoc" classifier
+JAR_FILE=$(ls target/tracing-opentelemetry-*.jar | grep --invert-match -e "sources" -e "javadoc")
+
+# Fail if there's a problem with how the script got the filename.
+# (Like, maybe there's an old snapshot getting in the way.)
+#
+# Use archaic option format for compatibility with Java 8.
+#   t is --list (List the table of contents for the archive)
+#   f is --file (Read from a file)
+jar tf "$JAR_FILE" > /dev/null
+
+echo "Scanning $JAR_FILE for unexpected packages or native libraries..."
+
+# We *want* grep to exit with a status code of 1 (nothing matched).
+set +e
+
+# Scan for unexpected packages.
+# Line ends with "/" == just a directory; don't care about it.
+# Line starts with "com/couchbase/" == it's our code, or something we've relocated.
+# Line starts with "couchbase/" == protostellar proto definitions.
+# Anything else is unexpected.
+jar tf "$JAR_FILE" | grep --invert-match -e "/$" -e "META-INF" -e "^com/couchbase/" -e "^couchbase/"
+if [ $? -ne 1 ]; then
+  echo "ERROR: Found unexpected packages in $JAR_FILE (see above)"
+  echo "Please exclude or relocate them, or update the shade-check.sh script to expect them."
+  exit 1
+fi
+
+# Scan for unexpected native libraries.
+jar tf "$JAR_FILE" | grep "META-INF/native/." | grep --invert-match -e "/$" -e "com_couchbase_client_core_deps_"
+if [ $? -ne 1 ]; then
+  echo "ERROR: Found unexpected native libraries in $JAR_FILE (see above)"
+  echo "Please exclude or relocate them, or update the shade-check.sh script to expect them."
+  exit 1
+fi
+
+echo "Scan complete. No un-relocated shaded libraries found. That's good!"