[clang] [lldb] [clang][AST] fix ast-print of extern <lang> with >=2 declarators, fixed (PR #93913)

[Chelsea Cassanova via cfe-commits]

chelcassanova wrote:

Hey! Looks like this commit broke some tests on the LLDB macOS buildbots: https://green.lab.llvm.org/job/llvm.org/view/LLDB/job/as-lldb-cmake/6805/console

```
Assertion failed: (!isUnbracedLanguageLinkage(DC) || SC == SC_None), function VarDecl, file Decl.cpp, line 2128.
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace.
Stack dump:
0.	<user expression 0>:1:1: current parser token 'sum'
1.	<lldb wrapper prefix>:44:1: parsing function body '$__lldb_expr'
2.	<lldb wrapper prefix>:44:1: in compound statement ('{}')
```

In the tests
```
lldb-api :: commands/expression/dont_allow_jit/TestAllowJIT.py
  lldb-api :: commands/expression/entry-bp/TestExprEntryBP.py
  lldb-api :: commands/expression/result_numbering/TestResultNumbering.py
```

https://github.com/llvm/llvm-project/pull/93913