[llvm] Reland of #108413: [Offload] Introduce offload-tblgen and initial new API implementation (PR #118503)

[Jan Patrick Lehr via llvm-commits]

jplehr wrote:

I think both build with `LLVM_ENABLE_SHARED` or whatever the CMake variable is called

```
9.370 [88/25/3417] Linking CXX executable /home/botworker/builds/openmp-offload-amdgpu-runtime-2/llvm.build/bin/offload-tblgen
FAILED: /home/botworker/builds/openmp-offload-amdgpu-runtime-2/llvm.build/bin/offload-tblgen 
: && /home/botworker/builds/openmp-offload-amdgpu-runtime-2/llvm.build/./bin/clang++ --target=x86_64-unknown-linux-gnu -fPIC -fno-semantic-interposition -fvisibility-inlines-hidden -Werror=date-time -Werror=unguarded-availability-new -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wmissing-field-initializers -Wimplicit-fallthrough -Wcovered-switch-default -Wno-noexcept-type -Wnon-virtual-dtor -Wdelete-non-virtual-dtor -Wsuggest-override -Wstring-conversion -Wmisleading-indentation -Wctad-maybe-unsupported -fdiagnostics-color -ffunction-sections -fdata-sections -O3 -DNDEBUG -Wl,--color-diagnostics    -Wl,--gc-sections offload/tools/offload-tblgen/CMakeFiles/offload-tblgen.dir/APIGen.cpp.o offload/tools/offload-tblgen/CMakeFiles/offload-tblgen.dir/EntryPointGen.cpp.o offload/tools/offload-tblgen/CMakeFiles/offload-tblgen.dir/FuncsGen.cpp.o offload/tools/offload-tblgen/CMakeFiles/offload-tblgen.dir/offload-tblgen.cpp.o offload/tools/offload-tblgen/CMakeFiles/offload-tblgen.dir/PrintGen.cpp.o -o /home/botworker/builds/openmp-offload-amdgpu-runtime-2/llvm.build/bin/offload-tblgen  -Wl,-rpath,"\$ORIGIN/../lib:/home/botworker/builds/openmp-offload-amdgpu-runtime-2/llvm.build/./lib:/home/botworker/builds/openmp-offload-amdgpu-runtime-2/llvm.build/lib"  /home/botworker/builds/openmp-offload-amdgpu-runtime-2/llvm.build/lib/libLLVMTableGen.so.20.0git  -Wl,-rpath-link,/home/botworker/builds/openmp-offload-amdgpu-runtime-2/llvm.build/lib && :
ld.lld: error: undefined symbol: llvm::raw_ostream::write(char const*, unsigned long)
>>> referenced by APIGen.cpp
>>>               offload/tools/offload-tblgen/CMakeFiles/offload-tblgen.dir/APIGen.cpp.o:(EmitOffloadAPI(llvm::RecordKeeper const&, llvm::raw_ostream&))
>>> referenced by APIGen.cpp
>>>               offload/tools/offload-tblgen/CMakeFiles/offload-tblgen.dir/APIGen.cpp.o:(EmitOffloadAPI(llvm::RecordKeeper const&, llvm::raw_ostream&))
>>> referenced by APIGen.cpp
>>>               offload/tools/offload-tblgen/CMakeFiles/offload-tblgen.dir/APIGen.cpp.o:(EmitOffloadAPI(llvm::RecordKeeper const&, llvm::raw_ostream&))
>>> referenced 123 more times
```

https://github.com/llvm/llvm-project/pull/118503