SwiftDriverExecution: add explicit dependency on libllbuild

The module directly imports libllbuild, and while the dependency
_should_ be available due to the dependency on `llbuildSwift`, this
ensures that we do not rely on ordering but rather the explicit
dependency is codified into the build graph.

Author: compnerd

Sources/SwiftDriverExecution/CMakeLists.txt

@@ -17,6 +17,7 @@ target_link_libraries(SwiftDriverExecution PUBLIC
   SwiftOptions
   SwiftDriver)
 target_link_libraries(SwiftDriverExecution PRIVATE
+  libllbuild
   llbuildSwift)
 
 set_property(GLOBAL APPEND PROPERTY SWIFTDRIVER_EXPORTS SwiftDriverExecution)