Added GPU test job limit to make it consistent with current config
https://github.com/llvm/llvm-zorg/blob/main/buildbot/osuosl/master/config/builders.py#L2027C31-L2027C77

An upcoming libc4GPU buildbot will be using this CMake cache file for
its build configuration.

PR #134713, which landed as 79cb6f05da37, causes this on my test
systems:

```
-- Building AMDGPU plugin for dlopened libhsa
-- Not generating AMDGPU tests, no supported devices detected. Use 'LIBOMPTARGET_FORCE_AMDGPU_TESTS' to override.
-- Building CUDA plugin for dlopened libcuda
-- Not generating NVIDIA tests, no supported devices detected. Use 'LIBOMPTARGET_FORCE_NVIDIA_TESTS' to override.
```

The problem is it cannot locate amdgpu-arch and nvptx-arch. This patch
enables it to.

I suspect there is more cleanup to do here. amdgpu-arch and nvptx-arch
do not appear to exist as cmake targets anymore, but there is still
cmake code here that looks for those targets.

Enable the LLVM_ENABLE_RUNTIMES=flang-rt build of the Fortran runtime
for the amdgpu-offload-* buildbots. This pre-population cmake cache
files is referred to by the llvm-zorg annotated builder factory
[script](https://github.com/llvm/llvm-zorg/blob/872f477610d83821c9f1368c969006789b21011b/zorg/buildbot/builders/annotated/amdgpu-offload-cmake.py#L26).

The corresponding change in llvm-zorg is
llvm/llvm-zorg#402

This reverts commit e296fb8ff6255b97db9ff6cd941acc730164b38f.

The worker of amdgpu-offload-rhel-8-cmake-build-only has been updated
with a newer version of Ninja that supports Fortran.

Reverts llvm/llvm-project#129692

The builder amdgpu-offload-rhel-8-cmake-build-only fails because its
version of Ninja is too old. At least Ninja 1.10 is required for its
support for dependencies between Fortran modules.

https://lab.llvm.org/buildbot/#/builders/204/builds/2696

Enable the LLVM_ENABLE_RUNTIMES=flang-rt build of the Fortran runtime
for the amdgpu-offload-* buildbots. This pre-population cmake cache
files is referred to by the llvm-zorg annotated builder factory
[script](https://github.com/llvm/llvm-zorg/blob/872f477610d83821c9f1368c969006789b21011b/zorg/buildbot/builders/annotated/amdgpu-offload-cmake.py#L26).

The corresponding change in llvm-zorg is
https://github.com/llvm/llvm-zorg/pull/402

Enable the SPIRV backend on the CMake-cache file buildbots.

Summary:
We originally wanted `-stdlib=libc++` by default so that it could use
offloading support in libc++, however this causes issues with out the
Offloading proejct itself is built. Is the user builds the LLVM libs
with libstdc++ then uses this cache it will enable this option by
default for the ensuing build of the offloading libraries with the newly
build clang. This will cause a lot of linker failured because the C++
library doesn't match.

Long term I think the proper solution to this is to make better use of
clang configuration files, but I don't know a good way to do that by
default. For now just make it build right.

This enables more projects in the CMake cache to add them to the
buildbot coverage in the AMDGPU buildbots.

This is the next step to move the CMake cache file builder closer to the
build configuration we care about downstream.