[clang] [clang][ssaf] Add EntityLinkage data structure (PR #181718)

[LLVM Continuous Integration via cfe-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `flang-x86_64-windows` running on `minipc-ryzen-win` while building `clang` at step 6 "build-unified-tree".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/166/builds/6580

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

```
Step 6 (build-unified-tree) failure: build (failure)
...
            _Iter=std::_Vector_const_iterator<std::_Vector_val<std::_Simple_types<Fortran::evaluate::SymbolRef>>>
        ]
..\llvm-project\flang\include\flang/Semantics/symbol.h(574): note: see the first reference to 'std::vector<Fortran::evaluate::SymbolRef,std::allocator<Fortran::evaluate::SymbolRef>>::insert' in 'Fortran::semantics::NamelistDetails::add_objects'
C:\Program Files\Microsoft Visual Studio\2022\Community\VC\Tools\MSVC\14.44.35207\include\vector(1282): note: see reference to function template instantiation 'void std::vector<Fortran::evaluate::SymbolRef,std::allocator<Fortran::evaluate::SymbolRef>>::_Insert_counted_range<const Fortran::common::Reference<const Fortran::semantics::Symbol>*>(std::_Vector_const_iterator<std::_Vector_val<std::_Simple_types<_Ty>>>,_Iter,const unsigned __int64)' being compiled
        with
        [
            _Ty=Fortran::evaluate::SymbolRef,
            _Iter=const Fortran::common::Reference<const Fortran::semantics::Symbol> *
        ]
237.817 [111/6/7419] Linking CXX executable bin\clang-import-test.exe
FAILED: [code=4294967295] bin/clang-import-test.exe 
C:\Windows\system32\cmd.exe /C "cd . && "C:\Program Files\CMake\bin\cmake.exe" -E vs_link_exe --msvc-ver=1944 --intdir=tools\clang\tools\clang-import-test\CMakeFiles\clang-import-test.dir --rc=C:\PROGRA~2\WI3CF2~1\10\bin\100261~1.0\x64\rc.exe --mt=C:\PROGRA~2\WI3CF2~1\10\bin\100261~1.0\x64\mt.exe --manifests  -- C:\PROGRA~1\MICROS~2\2022\COMMUN~1\VC\Tools\MSVC\1444~1.352\bin\Hostx64\x64\link.exe /nologo @CMakeFiles\clang-import-test.rsp  /out:bin\clang-import-test.exe /implib:lib\clang-import-test.lib /pdb:bin\clang-import-test.pdb /version:0.0 /machine:x64 /STACK:10000000 /INCREMENTAL:NO /subsystem:console && cd ."
LINK: command "C:\PROGRA~1\MICROS~2\2022\COMMUN~1\VC\Tools\MSVC\1444~1.352\bin\Hostx64\x64\link.exe /nologo @CMakeFiles\clang-import-test.rsp /out:bin\clang-import-test.exe /implib:lib\clang-import-test.lib /pdb:bin\clang-import-test.pdb /version:0.0 /machine:x64 /STACK:10000000 /INCREMENTAL:NO /subsystem:console /MANIFEST:EMBED,ID=1" failed (exit code 0) with the following output:


  Version 14.44.35222.0



  ExceptionCode            = C0000005

  ExceptionFlags           = 00000000

  ExceptionAddress         = 00007FF78C5357B3 (00007FF78C4E0000) "C:\PROGRA~1\MICROS~2\2022\COMMUN~1\VC\Tools\MSVC\1444~1.352\bin\Hostx64\x64\link.exe"

  NumberParameters         = 00000002

  ExceptionInformation[ 0] = 0

  ExceptionInformation[ 1] = 1410397FB3F



CONTEXT:

  Rax    = 0  R8     = 140AC73B4C0

  Rbx    = 0  R9     = 140FF95C30B

  Rcx    = 140FF9643CB  R10    = FEFEFEFEFEFEFEFF

  Rdx    = 1410397FB3F  R11    = 8080808080808080

  Rsp    = 8025FB1B0  R12    = 1

  Rbp    = 8025FB2F0  E13    = 1A8

  Rsi    = 1410397FB3F  R14    = 140AD757FC0


```

</details>

https://github.com/llvm/llvm-project/pull/181718