[flang] [llvm] [flang] implement show_descriptor intrinsic, a non-standard extension (PR #169137)

[Tom Stellard via llvm-commits]

tstellar wrote:

I'm seeing a build failure with the Windows release script that I think may be caused by this commit:
`flang-rt/unittests/Runtime/Descriptor.cpp(188,5): error: use of undeclared identifier 'ftruncate'`
Here is the full build log:
https://github.com/llvm/llvm-project/actions/runs/19842117405/job/56852610863

https://github.com/llvm/llvm-project/pull/169137