Fixes#123300
What is seen
```
clang-repl> int x = 42;
clang-repl> auto capture = [&]() { return x * 2; };
In file included from <<< inputs >>>:1:
input_line_4:1:17: error: non-local lambda expression cannot have a capture-default
1 | auto capture = [&]() { return x * 2; };
| ^
zsh: segmentation fault clang-repl --Xcc="-v"
(lldb) bt
* thread #1, queue = 'com.apple.main-thread', stop reason = EXC_BAD_ACCESS (code=1, address=0x8)
* frame #0: 0x0000000107b4f8b8 libclang-cpp.19.1.dylib`clang::IncrementalParser::CleanUpPTU(clang::PartialTranslationUnit&) + 988
frame #1: 0x0000000107b4f1b4 libclang-cpp.19.1.dylib`clang::IncrementalParser::ParseOrWrapTopLevelDecl() + 416
frame #2: 0x0000000107b4fb94 libclang-cpp.19.1.dylib`clang::IncrementalParser::Parse(llvm::StringRef) + 612
frame #3: 0x0000000107b52fec libclang-cpp.19.1.dylib`clang::Interpreter::ParseAndExecute(llvm::StringRef, clang::Value*) + 180
frame #4: 0x0000000100003498 clang-repl`main + 3560
frame #5: 0x000000018d39a0e0 dyld`start + 2360
```
Though the error is justified, we shouldn't be interested in exiting
through a segfault in such cases.
The issue is that empty named decls weren't being taken care of
resulting into this assert
c1a2292526/clang/include/clang/AST/DeclarationName.h (L503)
Can also be seen when the example is attempted through xeus-cpp-lite.
If we run into a first usage or definition of a mangled name, and
there's a DeferredDecl that associated with it, we should remember it we
need to emit it later on.
Without this patch, clang-repl hits a JIT symbol not found error:
clang-repl> extern "C" int printf(const char *, ...);
clang-repl> auto l1 = []() { printf("ONE\n"); return 42; };
clang-repl> auto l2 = []() { printf("TWO\n"); return 17; };
clang-repl> auto r1 = l1();
ONE
clang-repl> auto r2 = l2();
TWO
clang-repl> auto r3 = l2();
JIT session error: Symbols not found: [ l2 ]
error: Failed to materialize symbols: { (main,
{ r3, orc_init_func.incr_module_5, $.incr_module_5.inits.0 }) }
Signed-off-by: Jun Zhang <jun@junz.org>
Differential Revision: https://reviews.llvm.org/D130831
