[OpenMP] Add tool dependencies in runtimes mode

[jhuber6]

Summary

The OpenMP offloading device runtime depends on multiple tools. We
should ensure that these tools are build before invoking the OpenMP
build.

[tra]

LGTM with a couple of nits.

llvm/runtimes/CMakeLists.txt

365

Should AND OPENMP_ENABLE_LIBOMPTARGET) be moved to the top-level if?

367

Nit: stray <TAB> character.

[jhuber6]

llvm/runtimes/CMakeLists.txt

365

These dependencies are only relevant for libomptarget. So if we're only building libomp they can be ignored.

llvm/runtimes/CMakeLists.txt

 endfunction()
 
 if(runtimes)
   # Create a runtimes target that uses this file as its top-level CMake file.
   # The runtimes target is a configuration of all the runtime libraries
   # together in a single CMake invocation.
   set(extra_deps "")
   if("openmp" IN_LIST LLVM_ENABLE_RUNTIMES)
-    if(TARGET opt)
-      list(APPEND extra_deps opt)
-    endif()
-    if(TARGET llvm-link)
-      list(APPEND extra_deps llvm-link)
+    foreach(dep opt llvm-link llvm-extract clang clang-offload-packager)
+      if(TARGET ${dep} AND OPENMP_ENABLE_LIBOMPTARGET)
+        list(APPEND extra_deps ${dep})
       endif()
+    endforeach()
   endif()
   if("libc" IN_LIST LLVM_ENABLE_RUNTIMES AND 
       (LLVM_LIBC_FULL_BUILD OR LIBC_GPU_BUILD OR LIBC_GPU_ARCHITECTURES))
     if(TARGET libc-hdrgen)
       set(libc_tools libc-hdrgen)
       set(libc_cmake_args "-DLIBC_HDRGEN_EXE=$<TARGET_FILE:libc-hdrgen>"
                           "-DLLVM_LIBC_FULL_BUILD=ON")
       list(APPEND extra_deps ${libc_tools})