(cherry picked from commit 1127742e387ef78b91ec1e4cec0bb17b5e85666c)
This allows cargo metadata to operate on it without adding the source files to the build. (A choice which will save a few rebuilds of the manual) (cherry picked from commit 1779295f3e13cc15f8422d52a3753bb927ac8fa7)
(cherry picked from commit 19ed7bd655e72e10373f1afab5af214f2f47881e)
(cherry picked from commit 6c8e116e8bbaecce2b77fd9e0db89f366b57f9b6)