[libc] Add libc archive dependency on the header target

[phosek]

Summary

This ensures that libc headers are built and installed together with
the libc archive in the full build.

[phosek]

There may be a cleaner/more principled way, suggestions are welcome.

[sivachandra]

The idea was that install-libc is that one target that pulls everything into the installation. Can you give more detail about the behavior you are observing?

libc/lib/CMakeLists.txt

37

Does this really ensure installation of headers along with the archive?

[phosek]

In D158897#4618645, @sivachandra wrote:

The idea was that install-libc is that one target that pulls everything into the installation. Can you give more detail about the behavior you are observing?

I was seeing missing headers when doing a full build, but I can no longer reproduce this so it's possible that some of my other CMake changes addressed the actual issue.

libc/lib/CMakeLists.txt

add_entrypoint_library(
     DEPENDS
       ${${archive_2}}
   )
   set_target_properties(
     ${archive_1}
     PROPERTIES
       ARCHIVE_OUTPUT_NAME ${archive_0}
   )
+  if(LLVM_LIBC_FULL_BUILD)
+    add_dependencies(${archive_1} libc-headers)
+  endif()
   list(APPEND added_archive_targets ${archive_1})
 endforeach()
 
 if(LIBC_TARGET_TRIPLE)
   set(LIBC_INSTALL_LIBRARY_DIR lib${LLVM_LIBDIR_SUFFIX}/${LIBC_TARGET_TRIPLE})
 elseif(LLVM_ENABLE_PER_TARGET_RUNTIME_DIR AND NOT LIBC_GPU_BUILD)
   set(LIBC_INSTALL_LIBRARY_DIR
       lib${LLVM_LIBDIR_SUFFIX}/${LLVM_DEFAULT_TARGET_TRIPLE})