[flang] Force the use of intrinsic builtins in type_info

[luporl]

Summary

This ensures that the __Fortran_builtins module is always used
as an intrinsic module by __Fortran_type_info, which avoids issues
when, for instance, the intrinsic modules dir is present in the
include paths.

Fixes https://github.com/llvm/llvm-project/issues/63592

[klausler]

Make sure that everything builds with this change even with completely clean build and install directories. The use of "intrinsic" in USE statements in intrinsic modules is problematic when building intrinsic modules, since they depend on intrinsic modules that haven't been built and installed yet.

[luporl]

Everything built fine, even after removing build and install directories.

I guess it's because __fortran_builtins.mod is set as a dependency of __fortran_type_info in flang/tools/f18/CMakeLists.txt.

[klausler]

In D154452#4474848, @luporl wrote:

Everything built fine, even after removing build and install directories.

I guess it's because __fortran_builtins.mod is set as a dependency of __fortran_type_info in flang/tools/f18/CMakeLists.txt.

How does semantics find the module fortran_builtins.mod as an intrinsic module while building fortran_type_info, when there are no intrinsic modules installed anywhere yet?

[luporl]

In D154452#4474902, @klausler wrote:

In D154452#4474848, @luporl wrote:

Everything built fine, even after removing build and install directories.

I guess it's because __fortran_builtins.mod is set as a dependency of __fortran_type_info in flang/tools/f18/CMakeLists.txt.

How does semantics find the module fortran_builtins.mod as an intrinsic module while building fortran_type_info, when there are no intrinsic modules installed anywhere yet?

I haven't debugged semantics to confirm it, but it seems __fortran_builtins.mod is found because of the -module-dir flag. This is the command line used to build __fortran_type_info:

/home/leandro.lupori/git/flang-luporl/buildr/bin/flang-new -cpp -fsyntax-only -module-dir /home/leandro.lupori/git/flang-luporl/buildr/include/flang /home/leandro.lupori/git/flang-luporl/llvm-project/flang/module/__fortran_type_info.f90

flang/module/__fortran_type_info.f90

 !===-- module/__fortran_type_info.f90 --------------------------------------===!
 !
 ! Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 ! See https://llvm.org/LICENSE.txt for license information.
 ! SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 !
 !===------------------------------------------------------------------------===!
 
 ! Fortran definitions of runtime type description schemata.
 ! See flang/runtime/type-info.h for C++ perspective.
 ! The Semantics phase of the compiler requires the module file of this module
 ! in order to generate description tables for all other derived types.
 
 module __Fortran_type_info
 
-  use __Fortran_builtins, only: __builtin_c_ptr, __builtin_c_funptr
+  use, intrinsic :: __Fortran_builtins, only: __builtin_c_ptr, __builtin_c_funptr
 
   private
 
   integer, parameter :: int64 = selected_int_kind(18)
 
   type :: DerivedType
     ! "TBP" bindings appear first.  Inherited bindings, with overrides already
     ! applied, appear in the initial entries in the same order as they