The official LLVM and lldb builds use `LLVM_ENABLE_RPMALLOC`. This
changes the default CRT allocator to rpmalloc for performance reasons.
In doing so, it also changes the CRT linkage from dynamic (`/MD`) to
static (`/MT`).
Since the CRT is the one managing file descriptors on Windows, its
universe is now scoped to a module. For lldb, this means we have three
fd-spaces: the driver (lldb/lldb-dap), liblldb, and Python.
We usually pass files around as file descriptors. This breaks when we do
it between modules.
Fortunately, the C runtime provides us with helpers to translate between
the process scoped HANDLEs and file descriptors. This way, we can
allocate an fd for a handle passed across modules. For Python, there's
the [`msvcrt`](https://docs.python.org/3/library/msvcrt.html) library we
can use to translate.
Fixes#216679.
(cherry picked from commit 1ca6698be7708121f987d0acf896c7dc4cf63a51)
Nerixyz
28a01b03e1