[llvm] Reland #2 - [Offload] Introduce offload-tblgen and initial new API implementation (#108413. #117704) (PR #117894)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `openmp-offload-libc-amdgpu-runtime` running on `omp-vega20-1` while building `offload` at step 7 "Add check check-offload".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/73/builds/9293

<details>
<summary>Here is the relevant piece of the build log for the reference</summary>

```
Step 7 (Add check check-offload) failure: test (failure)
******************** TEST 'libomptarget :: amdgcn-amd-amdhsa :: tools/offload-tblgen/default_returns.td' FAILED ********************
Exit Code: 2

Command Output (stdout):
--
# RUN: at line 1
/home/ompworker/bbot/openmp-offload-libc-amdgpu-runtime/llvm.build/./bin/offload-tblgen -gen-api -I /home/ompworker/bbot/openmp-offload-libc-amdgpu-runtime/llvm.src/offload/test/tools/offload-tblgen/../../../new-api/API /home/ompworker/bbot/openmp-offload-libc-amdgpu-runtime/llvm.src/offload/test/tools/offload-tblgen/default_returns.td | /home/ompworker/bbot/openmp-offload-libc-amdgpu-runtime/llvm.build/./bin/FileCheck /home/ompworker/bbot/openmp-offload-libc-amdgpu-runtime/llvm.src/offload/test/tools/offload-tblgen/default_returns.td --check-prefix=CHECK-API
# executed command: /home/ompworker/bbot/openmp-offload-libc-amdgpu-runtime/llvm.build/./bin/offload-tblgen -gen-api -I /home/ompworker/bbot/openmp-offload-libc-amdgpu-runtime/llvm.src/offload/test/tools/offload-tblgen/../../../new-api/API /home/ompworker/bbot/openmp-offload-libc-amdgpu-runtime/llvm.src/offload/test/tools/offload-tblgen/default_returns.td
# .---command stderr------------
# | /home/ompworker/bbot/openmp-offload-libc-amdgpu-runtime/llvm.src/offload/test/tools/offload-tblgen/default_returns.td:7:9: error: could not find include file 'APIDefs.td'
# | include "APIDefs.td"
# |         ^
# | /home/ompworker/bbot/openmp-offload-libc-amdgpu-runtime/llvm.src/offload/test/tools/offload-tblgen/default_returns.td:7:9: error: Unexpected token at top level
# | include "APIDefs.td"
# |         ^
# `-----------------------------
# error: command failed with exit status: 1
# executed command: /home/ompworker/bbot/openmp-offload-libc-amdgpu-runtime/llvm.build/./bin/FileCheck /home/ompworker/bbot/openmp-offload-libc-amdgpu-runtime/llvm.src/offload/test/tools/offload-tblgen/default_returns.td --check-prefix=CHECK-API
# .---command stderr------------
# | FileCheck error: '<stdin>' is empty.
# | FileCheck command line:  /home/ompworker/bbot/openmp-offload-libc-amdgpu-runtime/llvm.build/./bin/FileCheck /home/ompworker/bbot/openmp-offload-libc-amdgpu-runtime/llvm.src/offload/test/tools/offload-tblgen/default_returns.td --check-prefix=CHECK-API
# `-----------------------------
# error: command failed with exit status: 2

--

********************


```

</details>

https://github.com/llvm/llvm-project/pull/117894