git: ignore in files in the Runtimes

We include some template files in the runtime build and we should not
commit those as we currently are using `Resync.cmake` to synchronise the
directory.

Author: compnerd

.gitignore

@@ -96,3 +96,4 @@ Runtimes/**/*.yaml
 Runtimes/**/*.inc
 Runtimes/**/*.json
 Runtimes/**/*.modulemap
+Runtimes/**/*.in