[CMake] Use add_dependencies in add_llvm_install_targets

[xiaobai]

Summary

The CMake documentation says that the DEPENDS field of
add_custom_target is for files and output of custom commands. Adding a
dependency on a target should be done with add_dependencies.

[compnerd]

*sigh* CMake - that is subtle.

[smeenai]

LGTM, thanks!

cmake/modules/AddLLVM.cmake

function(add_llvm_install_targets target)
   cmake_parse_arguments(ARG "" "COMPONENT;PREFIX" "DEPENDS" ${ARGN})
   if(ARG_COMPONENT)
     set(component_option -DCMAKE_INSTALL_COMPONENT="${ARG_COMPONENT}")
   endif()
   if(ARG_PREFIX)
     set(prefix_option -DCMAKE_INSTALL_PREFIX="${ARG_PREFIX}")
   endif()
 
+  set(file_dependencies)
+  set(target_dependencies)
+  foreach(dependency ${ARG_DEPENDS})
+    if(TARGET ${dependency})
+      list(APPEND target_dependencies ${dependency})
+    else()
+      list(APPEND file_dependencies ${dependency})
+    endif()
+  endforeach()
+
   add_custom_target(${target}
-                    DEPENDS ${ARG_DEPENDS}
+                    DEPENDS ${file_dependencies}
                     COMMAND "${CMAKE_COMMAND}"
                             ${component_option}
                             ${prefix_option}
                             -P "${CMAKE_BINARY_DIR}/cmake_install.cmake"
                     USES_TERMINAL)
   add_custom_target(${target}-stripped
-                    DEPENDS ${ARG_DEPENDS}
+                    DEPENDS ${file_dependencies}
                     COMMAND "${CMAKE_COMMAND}"
                             ${component_option}
                             ${prefix_option}
                             -DCMAKE_INSTALL_DO_STRIP=1
                             -P "${CMAKE_BINARY_DIR}/cmake_install.cmake"
                     USES_TERMINAL)
+  if(target_dependencies)
+    add_dependencies(${target} ${target_dependencies})
+    add_dependencies(${target}-stripped ${target_dependencies})
+  endif()
 endfunction()
 
 macro(add_llvm_library name)
   cmake_parse_arguments(ARG
     "SHARED;BUILDTREE_ONLY;MODULE"
     ""
     ""
     ${ARGN})