[OpenMP] Change build of OpenMP device runtime to be a separate runtime (#136729)

Summary:
Currently we build the OpenMP device runtime as part of the `offload/`
project. This is problematic because it has several restrictions when
compared to the normal offloading runtime. It can only be built with an
up-to-date clang and we need to set the target appropriately. Currently
we hack around this by creating the compiler invocation manually, but
this patch moves it into a separate runtimes build.

This follows the same build we use for libc, libc++, compiler-rt, and
flang-rt. This also moves it from `offload/` into `openmp/` because it
is still the `openmp/` runtime and I feel it is more appropriate. We do
want a generic `offload/` library at some point, but it would be trivial
to then add that as a separate library now that we have the
infrastructure that makes adding these new libraries trivial.

This most importantly will require that users update their build
configs, mostly adding the following lines at a minimum. I was debating
whether or not I should 'auto-upgrade' this, but I just went with a
warning.

```
    -DLLVM_RUNTIME_TARGETS='default;amdgcn-amd-amdhsa;nvptx64-nvidia-cuda'     \
    -DRUNTIMES_nvptx64-nvidia-cuda_LLVM_ENABLE_RUNTIMES=openmp \
    -DRUNTIMES_amdgcn-amd-amdhsa_LLVM_ENABLE_RUNTIMES=openmp \
```

This also changed where the `.bc` version of the library lives, but it's
still created.

1 files changed, 0 insertions, 44 deletions

diff --git a/offload/DeviceRTL/include/Debug.h b/offload/DeviceRTL/include/Debug.h
deleted file mode 100644
index 98d0fa498d95..000000000000
--- a/offload/DeviceRTL/include/Debug.h
+++ /dev/null
@@ -1,44 +0,0 @@
-//===-------- Debug.h ---- Debug utilities ------------------------ C++ -*-===//
-//
-// 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
-//
-//===----------------------------------------------------------------------===//
-//
-//
-//===----------------------------------------------------------------------===//
-
-#ifndef OMPTARGET_DEVICERTL_DEBUG_H
-#define OMPTARGET_DEVICERTL_DEBUG_H
-
-#include "Configuration.h"
-#include "LibC.h"
-
-/// Assertion
-///
-/// {
-extern "C" {
-void __assert_assume(bool condition);
-void __assert_fail(const char *expr, const char *file, unsigned line,
-                   const char *function);
-void __assert_fail_internal(const char *expr, const char *msg, const char *file,
-                            unsigned line, const char *function);
-}
-
-#define ASSERT(expr, msg)                                                      \
-  {                                                                            \
-    if (config::isDebugMode(DeviceDebugKind::Assertion) && !(expr))            \
-      __assert_fail_internal(#expr, msg, __FILE__, __LINE__,                   \
-                             __PRETTY_FUNCTION__);                             \
-    else                                                                       \
-      __assert_assume(expr);                                                   \
-  }
-#define UNREACHABLE(msg)                                                       \
-  printf(msg);                                                                 \
-  __builtin_trap();                                                            \
-  __builtin_unreachable();
-
-///}
-
-#endif