Fix include path error in mkdocs.sh introduced in 247cd3381745

Unfortunately in commit 247cd33817457789645827a52d79a1876b9760a3 I
mistakenly included the directories wrongly. This fixes this.

Change-Id: I91193321d1264985eab4865ca05adeab96401b2f
Reviewed-on: https://gerrit.libreoffice.org/7669
Reviewed-by: Markus Mohrhard <markus.mohrhard@googlemail.com>
Tested-by: Markus Mohrhard <markus.mohrhard@googlemail.com>
diff --git a/solenv/bin/mkdocs.sh b/solenv/bin/mkdocs.sh
index 93f502f..888521b 100755
--- a/solenv/bin/mkdocs.sh
+++ b/solenv/bin/mkdocs.sh
@@ -164,7 +164,7 @@ do
  fi

  if [ -d "include/$PROJECT" ]; then
      PROJECT_INCLUDE="$PROJECT_INCLUDE $PROJECT_INCLUDE"
      PROJECT_INCLUDE="$PROJECT_INCLUDE include/$PROJECT"
  fi

  DOXYGEN_INPUT=`printf "%s" "$PROJECT/source $PROJECT_INCLUDE"`