[flang] [clang] [llvm] [clang-tools-extra] [flang] Add EXECUTE_COMMAND_LINE runtime and lowering intrinsics implementation (PR #74077)

[Yi Wu via cfe-commits]

yi-wu-arm wrote:

Hi, @jeanPerier welcome back! I've made quite a few changes, mainly on memory allocate and deallocate, test improvements, and have moved some commonly used descriptor functions into `tools.cpp` to re-use some code instead of creating duplicates of them. Could you review the recent changes? Thanks in advance!

https://github.com/llvm/llvm-project/pull/74077