Also checkout /sitemap.xml during release

Fixes pmd#1328

.travis/release.sh

@@ -77,7 +77,8 @@ mkdir pmd.github.io
     git config user.email "[email protected]"
     git config core.sparsecheckout true
     git remote add origin [email protected]:pmd/pmd.github.io.git
-    echo "latest/" > .git/info/sparse-checkout
+    echo "/latest/" > .git/info/sparse-checkout
+    echo "/sitemap.xml" >> .git/info/sparse-checkout
     git pull --depth=1 origin master
     log_info "Copying documentation from ../docs/pmd-doc-${RELEASE_VERSION}/ to pmd-${RELEASE_VERSION}/ ..."
     rsync -ah --stats ../docs/pmd-doc-${RELEASE_VERSION}/ pmd-${RELEASE_VERSION}/

docs/pages/release_notes.md

@@ -29,6 +29,7 @@ This is a {{ site.pmd.release_type }} release.
 *   all
     *   [#1284](https://github.com/pmd/pmd/issues/1284): \[doc] Keep record of every currently deprecated API
     *   [#1318](https://github.com/pmd/pmd/issues/1318): \[test] Kotlin DSL to ease test writing
+    *   [#1328](https://github.com/pmd/pmd/issues/1328): \[ci] Building docs for release fails
     *   [#1341](https://github.com/pmd/pmd/issues/1341): \[doc] Documentation Error with Regex Properties
 *   java
     *   [#1460](https://github.com/pmd/pmd/issues/1460): \[java] Intermittent PMD failure : PMD processing errors while no violations reported