test(Makefile): add validate-docx-golden-test2

Add a validation rule based on OOXML-Validator which uses the
Open-XML-SDK shipped and maintained as part of dotnet.

This catches a few more issues compared to the .xsd.

Unfortunately currently this executable always exits with 0 even when
validation failed. That can be fixed later by invoking it from a script.

Signed-off-by: Edwin Török <edwin@etorok.net>

tools/validate-docx2.sh

@@ -0,0 +1,25 @@
+#!/bin/sh
+
+# based on validate-docx.sh, and adapted for OOXMLValidatorCLI
+# Modified by edwintorok from https://github.com/devoidfury/docx-validator
+# to look at more files than just document.xml.
+# Further modified by jgm for portability.
+
+tmpdir=$(mktemp -d)
+error_files=""
+errors=0
+VALIDATOR=OOXML-Validator/bin/Release/*/OOXMLValidatorCLI
+
+for file in "$@"; do
+  file_errors=0
+  echo "*** Checking $file"
+  dotnet $(VALIDATOR) "${file}" 2>&1 || file_errors=1
+  if [ $file_errors -gt 0 ]; then
+      errors=$((file_errors + errors))
+      error_files="$error_files\n$file"
+  fi
+done
+if [ $errors -gt 0 ]; then
+   echo "These files failed validation:$error_files"
+fi
+exit $errors