[clang] [flang] [llvm] [openmp] [Flang][OpenMP] Move builtin .mod generation into runtimes (PR #137828)

[Kelvin Li via cfe-commits]

kkwli wrote:

I encounter the following issue when building flang-rt.
```
[29/50] Building Fortran object flang-rt/...lang_rt.runtime.dir/ieee_arithmetic.f90.
FAILED: flang-rt/lib/runtime/CMakeFiles/obj.flang_rt.runtime.dir/ieee_arithmetic.f90.o lib/clang/22/finclude/powerpc64le-unknown-linux-gnu/ieee_arithmetic.mod 
/scratch/kli/wrk/f/build-flang-local/bin/flang -I/scratch/kli/llvm-project/flang-rt/lib/runtime -I/scratch/kli/llvm-project/flang-rt/include -I/scratch/kli/llvm-project/flang-rt/../flang/include -I/scratch/kli/wrk/f/build-flang-rt-local-standalone/flang-rt -module-dirlib/clang/22/finclude/powerpc64le-unknown-linux-gnu -fPIC -mmlir -ignore-missing-type-desc -Xflang -fno-reformat -fno-lto "-D_GLIBCXX_THROW_OR_ABORT(_EXC)=(__builtin_abort())" -fintrinsic-modules-path=/scratch/kli/wrk/f/build-flang-rt-local-standalone/lib/clang/22/finclude/powerpc64le-unknown-linux-gnu -ffixed-line-length-72 -c flang-rt/lib/runtime/CMakeFiles/obj.flang_rt.runtime.dir/ieee_arithmetic.f90-pp.f90 -o flang-rt/lib/runtime/CMakeFiles/obj.flang_rt.runtime.dir/ieee_arithmetic.f90.o
error: Semantic errors in flang-rt/lib/runtime/CMakeFiles/obj.flang_rt.runtime.dir/ieee_arithmetic.f90-pp.f90
./flang-rt/lib/runtime/CMakeFiles/obj.flang_rt.runtime.dir/ieee_arithmetic.f90-pp.f90:117:51: error: REAL(KIND=10) is not an enabled type for this target
  elemental logical function ieee_is_finite_a10(x); real(10), intent(in) :: x;
                                                    ^^^^^^^^^^^^^^^^^^^^^^^^^
[47/50] Building CXX object flang-rt/lib/....flang_rt.runtime.dir/descriptor-io.cpp.
ninja: build stopped: subcommand failed.

```

https://github.com/llvm/llvm-project/pull/137828