rules: Fix name of ghc-boot-th library

There was a missing `#`. Hadrian couldn't come soon enough.

(cherry picked from commit a54d87a9)

rules/foreachLibrary.mk

@@ -38,7 +38,7 @@
 define foreachLibrary
 # $1 = function to call for each library
 # We will give it the package path and the tag as arguments
-$$(foreach hashline,libraries/ghc-boot-th-#no-remote-repo#no-vcs            \
+$$(foreach hashline,libraries/ghc-boot-th#-#no-remote-repo#no-vcs           \
                     libraries/ghc-boot#-#no-remote-repo#no-vcs              \
                     libraries/ghci#-#no-remote-repo#no-vcs                  \
                     libraries/base#-#no-remote-repo#no-vcs                  \