[libcxx] Move the libc++ header paths to the common location

[phosek]

Summary

This change moves all libc++ header paths to the common location to
simplify future maintenance.

[ldionne]

libcxx/CMakeLists.txt

402

Can't we always do set(LIBCXX_HEADER_DIR "${CMAKE_BINARY_DIR}/something-private/include/c++/v1")? The place where we stage the headers is an implementation detail of the libc++ build anyway, so it shouldn't matter to any other project.

libcxx/include/CMakeLists.txt

250

Why don't we hardcode ${LIBCXX_INSTALL_HEADER_DIR} as include/c++/v1 here? I don't see the point in having this additional indirection.

[phosek]

libcxx/include/CMakeLists.txt

250

See D89013 where I build the per-target config support on top of this patch.

[phosek]

Combined into D89013.

libcxx/CMakeLists.txt

 #===============================================================================
 
 set(LIBCXX_SOURCE_DIR  ${CMAKE_CURRENT_SOURCE_DIR})
 set(LIBCXX_BINARY_DIR  ${CMAKE_CURRENT_BINARY_DIR})
 set(LIBCXX_BINARY_INCLUDE_DIR "${LIBCXX_BINARY_DIR}/include/c++build")
 
 if(LLVM_ENABLE_PER_TARGET_RUNTIME_DIR AND NOT APPLE)
   set(LIBCXX_LIBRARY_DIR ${LLVM_LIBRARY_OUTPUT_INTDIR}/${LLVM_DEFAULT_TARGET_TRIPLE}/c++)
-  set(LIBCXX_HEADER_DIR ${LLVM_BINARY_DIR})
+  set(LIBCXX_HEADER_DIR ${LLVM_BINARY_DIR}/include/c++/v1)
   set(LIBCXX_INSTALL_LIBRARY_DIR lib${LLVM_LIBDIR_SUFFIX}/${LLVM_DEFAULT_TARGET_TRIPLE}/c++)
+  set(LIBCXX_INSTALL_HEADER_DIR include/c++/v1)
   if(LIBCXX_LIBDIR_SUBDIR)
     string(APPEND LIBCXX_LIBRARY_DIR /${LIBCXX_LIBDIR_SUBDIR})
     string(APPEND LIBCXX_INSTALL_LIBRARY_DIR /${LIBCXX_LIBDIR_SUBDIR})
   endif()
 elseif(LLVM_LIBRARY_OUTPUT_INTDIR)
   set(LIBCXX_LIBRARY_DIR ${LLVM_LIBRARY_OUTPUT_INTDIR})
-  set(LIBCXX_HEADER_DIR  ${LLVM_BINARY_DIR})
+  set(LIBCXX_HEADER_DIR  ${LLVM_BINARY_DIR}/include/c++/v1)
   set(LIBCXX_INSTALL_LIBRARY_DIR lib${LIBCXX_LIBDIR_SUFFIX})
+  set(LIBCXX_INSTALL_HEADER_DIR include/c++/v1)
 else()
   set(LIBCXX_LIBRARY_DIR ${CMAKE_BINARY_DIR}/lib${LIBCXX_LIBDIR_SUFFIX})
-  set(LIBCXX_HEADER_DIR  ${CMAKE_BINARY_DIR})
+  set(LIBCXX_HEADER_DIR  ${CMAKE_BINARY_DIR}/include/c++/v1)
   set(LIBCXX_INSTALL_LIBRARY_DIR lib${LIBCXX_LIBDIR_SUFFIX})
+  set(LIBCXX_INSTALL_HEADER_DIR include/c++/v1)
 endif()
 
 file(MAKE_DIRECTORY "${LIBCXX_BINARY_INCLUDE_DIR}")
 
 set(LIBCXX_INSTALL_PREFIX "" CACHE STRING "Define libc++ destination prefix.")
 set(LIBCXX_INSTALL_HEADER_PREFIX "" CACHE STRING "Define libc++ header destination prefix.")
 
 set(CMAKE_ARCHIVE_OUTPUT_DIRECTORY ${LIBCXX_LIBRARY_DIR})

libcxx/include/CMakeLists.txt

add_custom_command(OUTPUT ${LIBCXX_BINARY_DIR}/__generated_config
   DEPENDS ${LIBCXX_SOURCE_DIR}/include/__config
           ${LIBCXX_BINARY_DIR}/__config_site
 )
 # Add a target that executes the generation commands.
 add_custom_target(cxx-generated-config ALL
   DEPENDS ${LIBCXX_BINARY_DIR}/__generated_config)
 
 if(LIBCXX_HEADER_DIR)
-  set(output_dir ${LIBCXX_HEADER_DIR}/include/c++/v1)
-
   set(out_files)
   foreach(f ${files})
     set(src ${CMAKE_CURRENT_SOURCE_DIR}/${f})
-    set(dst ${output_dir}/${f})
+    set(dst ${LIBCXX_HEADER_DIR}/${f})
     add_custom_command(OUTPUT ${dst}
       DEPENDS ${src}
       COMMAND ${CMAKE_COMMAND} -E copy_if_different ${src} ${dst}
       COMMENT "Copying CXX header ${f}")
     list(APPEND out_files ${dst})
   endforeach()
 
   # Copy the generated header as __config into build directory.
   set(src ${LIBCXX_BINARY_DIR}/__generated_config)
-  set(dst ${output_dir}/__config)
+  set(dst ${LIBCXX_HEADER_DIR}/__config)
   add_custom_command(OUTPUT ${dst}
       DEPENDS ${src} cxx-generated-config
       COMMAND ${CMAKE_COMMAND} -E copy_if_different ${src} ${dst}
       COMMENT "Copying CXX __config")
   list(APPEND out_files ${dst})
   add_custom_target(generate-cxx-headers DEPENDS ${out_files})
 
   add_library(cxx-headers INTERFACE)
   add_dependencies(cxx-headers generate-cxx-headers ${LIBCXX_CXX_ABI_HEADER_TARGET})
   # TODO: Use target_include_directories once we figure out why that breaks the runtimes build
   if("${CMAKE_CXX_COMPILER_ID}" STREQUAL "MSVC" OR "${CMAKE_CXX_SIMULATE_ID}" STREQUAL "MSVC")
-    target_compile_options(cxx-headers INTERFACE /I "${output_dir}")
+    target_compile_options(cxx-headers INTERFACE /I "${LIBCXX_HEADER_DIR}")
   else()
-    target_compile_options(cxx-headers INTERFACE -I "${output_dir}")
+    target_compile_options(cxx-headers INTERFACE -I "${LIBCXX_HEADER_DIR}")
   endif()
 
   # Make sure the generated __config_site header is included when we build the library.
   if("${CMAKE_CXX_COMPILER_ID}" STREQUAL "MSVC" OR "${CMAKE_CXX_SIMULATE_ID}" STREQUAL "MSVC")
     target_compile_options(cxx-headers INTERFACE /FI "${LIBCXX_BINARY_DIR}/__config_site")
   else()
     target_compile_options(cxx-headers INTERFACE -include "${LIBCXX_BINARY_DIR}/__config_site")
   endif()
 else()
   add_library(cxx-headers INTERFACE)
 endif()
 
 if (LIBCXX_INSTALL_HEADERS)
   foreach(file ${files})
     get_filename_component(dir ${file} DIRECTORY)
     install(FILES ${file}
-      DESTINATION ${LIBCXX_INSTALL_HEADER_PREFIX}include/c++/v1/${dir}
+      DESTINATION ${LIBCXX_INSTALL_HEADER_PREFIX}${LIBCXX_INSTALL_HEADER_DIR}/${dir}
       COMPONENT cxx-headers
       PERMISSIONS OWNER_READ OWNER_WRITE GROUP_READ WORLD_READ
     )
   endforeach()
 
   # Install the generated header as __config.
   install(FILES ${LIBCXX_BINARY_DIR}/__generated_config
     DESTINATION ${LIBCXX_INSTALL_HEADER_PREFIX}include/c++/v1