[AST] Remove implicit includes from introspection generation.

[njames93]

Summary

Run ast dump twice with implicit includes defined and not defined. This increases coverage as some systems require them, others will fail with them.

[njames93]

Factor out changes

[njames93]

The old impl for me was resulting in these kinds of errors during parsing.

/usr/include/c++/10/cstdint:52:11: error: no member named 'int_fast8_t' in the global namespace
  using ::int_fast8_t;
        ~~^

After removing the implicit includes, these errors went away and generation completed as intended.

[njames93]

Run 2 invocations, one with implicit includes, one without them. If either has no errors the json will be generated, otherwise an empty implementation will be emitted.
Some systems seem to require the implicit includes, others, including mine, will fail with them defined.

[steveire]

In D100319#2697017, @njames93 wrote:

Run 2 invocations, one with implicit includes, one without them. If either has no errors the json will be generated, otherwise an empty implementation will be emitted.
Some systems seem to require the implicit includes, others, including mine, will fail with them defined.

Instead of running it twice, it would be better if we understood better what the problem is.

I can't reproduce any problem with the implicit includes present. Can you reduce the code being compiled by the tool to find out why their presence causes a problem?

clang/lib/Tooling/CMakeLists.txt

else()
   # internal hidden setting to override.
   # When the processing is disabled, a trivial/empty JSON
   # file is generated by clang-ast-dump and generate_cxx_src_locs.py
   # generates the same API, but with a trivial implementation.
   option(CLANG_TOOLING_BUILD_AST_INTROSPECTION "Enable AST introspection" TRUE)
 
   set(skip_expensive_processing $<OR:$<CONFIG:Debug>,$<NOT:$<BOOL:${CLANG_TOOLING_BUILD_AST_INTROSPECTION}>>>)
 
-
-  set(implicitDirs)
-  foreach(implicitDir ${CMAKE_CXX_IMPLICIT_INCLUDE_DIRECTORIES})
-    list(APPEND implicitDirs -I ${implicitDir})
-  endforeach()
-
   add_custom_command(
       COMMENT Generate ASTNodeAPI.json
       OUTPUT ${CMAKE_CURRENT_BINARY_DIR}/ASTNodeAPI.json
       DEPENDS clang-ast-dump clang-resource-headers
       COMMAND
       $<TARGET_FILE:clang-ast-dump>
         # Skip this in debug mode because parsing AST.h is too slow
         --skip-processing=${skip_expensive_processing}
         -I ${CMAKE_BINARY_DIR}/lib/clang/${CLANG_VERSION}/include
         -I ${CMAKE_SOURCE_DIR}/../clang/include
         -I ${CMAKE_BINARY_DIR}/tools/clang/include
         -I ${CMAKE_BINARY_DIR}/include
         -I ${CMAKE_SOURCE_DIR}/include
-        ${implicitDirs}
         --json-output-path ${CMAKE_CURRENT_BINARY_DIR}/ASTNodeAPI.json
   )
 
   add_custom_target(run-ast-api-dump-tool
       DEPENDS ${CMAKE_CURRENT_BINARY_DIR}/ASTNodeAPI.json
   )
 
   add_custom_command(