[build-script] Stop installing the llbuildSwift library that is no longer used

Author: finagolfin

utils/build-script-impl

@@ -2984,7 +2984,7 @@ for host in "${ALL_HOSTS[@]}"; do
                 if [[ -z "${INSTALL_LLBUILD}" ]] ; then
                     continue
                 fi
-                INSTALL_TARGETS="install-swift-build-tool install-libllbuildSwift"
+                INSTALL_TARGETS="install-swift-build-tool"
                 ;;
             # Products from this here install themselves; they don't fall-through.
             lldb)