Hadrian: Track RTS library symlink targets

We create some symlinks to the rts library files with without the dummy version number. We do this for backwards compatibility reasons. Previously we used createFileLinkUntracked to avoid needing the target of the symlink: the rts library file. This was necessary, otherwise the the build rules form a cycle: library file -> symlink -> back to library file. Unfortunately, the untracked version leads to some build errors. To fix this the cycle in the rules must be broken. In this MR the need of the symlink is moved to just after needing the library file (instead of as a sub rule of the library file rule).