[clang-check][Syntax] Assertion `Arrow->kind() == tok::arrow` failed in buildTrailingReturn when dumping syntax tree for trailing return type

This input is generated by a fuzzer.
```c
auto foo() -> bar {
}
```

use
```
clang-check
--syntax-tree-dump
-- -xc++ -std=c++23
```
stacktrace:
```
clang-check: /home/ubuntu2404/llvm-project-196067/clang/lib/Tooling/Syntax/BuildTree.cpp:1633: clang::syntax::TrailingReturnType* {anonymous}::BuildTreeVisitor::buildTrailingReturn(clang::FunctionProtoTypeLoc): Assertion `Arrow->kind() == tok::arrow' failed.
#0 0x0000612f2ee031f1 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/home/ubuntu2404/build-196067-assert/bin/clang-check+0x96d1f1)
#1 0x0000612f2edffdac llvm::sys::RunSignalHandlers() (/home/ubuntu2404/build-196067-assert/bin/clang-check+0x969dac)
#2 0x0000612f2edfff0c SignalHandler(int, siginfo_t*, void*) Signals.cpp:0:0
#3 0x00007a0c3fe45330 (/lib/x86_64-linux-gnu/libc.so.6+0x45330)
#4 0x00007a0c3fe9eb2c __pthread_kill_implementation ./nptl/pthread_kill.c:44:76
#5 0x00007a0c3fe9eb2c __pthread_kill_internal ./nptl/pthread_kill.c:78:10
#6 0x00007a0c3fe9eb2c pthread_kill ./nptl/pthread_kill.c:89:10
#7 0x00007a0c3fe4527e raise ./signal/../sysdeps/posix/raise.c:27:6
#8 0x00007a0c3fe288ff abort ./stdlib/abort.c:81:7
#9 0x00007a0c3fe2881b _nl_load_domain ./intl/loadmsgcat.c:1177:9
#10 0x00007a0c3fe3b517 (/lib/x86_64-linux-gnu/libc.so.6+0x3b517)
#11 0x0000612f2f1a31bf (/home/ubuntu2404/build-196067-assert/bin/clang-check+0xd0d1bf)
#12 0x0000612f2f1a40f5 clang::RecursiveASTVisitor<(anonymous namespace)::BuildTreeVisitor>::TraverseTypeLoc(clang::TypeLoc, bool) (.constprop.0) BuildTree.cpp:0:0
#13 0x0000612f2f1b559f clang::RecursiveASTVisitor<(anonymous namespace)::BuildTreeVisitor>::TraverseFunctionHelper(clang::FunctionDecl*) BuildTree.cpp:0:0
#14 0x0000612f2f1a1ddc clang::RecursiveASTVisitor<(anonymous namespace)::BuildTreeVisitor>::TraverseDecl(clang::Decl*) BuildTree.cpp:0:0
#15 0x0000612f2f1a2aea clang::RecursiveASTVisitor<(anonymous namespace)::BuildTreeVisitor>::TraverseDeclContextHelper(clang::DeclContext*) BuildTree.cpp:0:0
#16 0x0000612f2f1bb83b clang::RecursiveASTVisitor<(anonymous namespace)::BuildTreeVisitor>::TraverseTranslationUnitDecl(clang::TranslationUnitDecl*) BuildTree.cpp:0:0
#17 0x0000612f2f1a2439 clang::syntax::buildSyntaxTree(clang::syntax::Arena&, clang::syntax::TokenBufferTokenManager&, clang::ASTContext&) (/home/ubuntu2404/build-196067-assert/bin/clang-check+0xd0c439)
#18 0x0000612f2e8964af (anonymous namespace)::DumpSyntaxTree::CreateASTConsumer(clang::CompilerInstance&, llvm::StringRef)::Consumer::HandleTranslationUnit(clang::ASTContext&) ClangCheck.cpp:0:0
#19 0x0000612f306ccf9c clang::ParseAST(clang::Sema&, bool, bool) (/home/ubuntu2404/build-196067-assert/bin/clang-check+0x2236f9c)
#20 0x0000612f2ee5a271 clang::FrontendAction::Execute() (/home/ubuntu2404/build-196067-assert/bin/clang-check+0x9c4271)
#21 0x0000612f2eea6308 clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) (/home/ubuntu2404/build-196067-assert/bin/clang-check+0xa10308)
#22 0x0000612f2f182cb7 clang::tooling::FrontendActionFactory::runInvocation(std::shared_ptr, clang::FileManager*, std::shared_ptr, clang::DiagnosticConsumer*) (/home/ubuntu2404/build-196067-assert/bin/clang-check+0xceccb7)
#23 0x0000612f2f17cb2a clang::tooling::ToolInvocation::runInvocation(char const*, clang::driver::Compilation*, std::shared_ptr, std::shared_ptr) (/home/ubuntu2404/build-196067-assert/bin/clang-check+0xce6b2a)
#24 0x0000612f2f17f1e2 clang::tooling::ToolInvocation::run() (/home/ubuntu2404/build-196067-assert/bin/clang-check+0xce91e2)
#25 0x0000612f2f180e19 clang::tooling::ClangTool::run(clang::tooling::ToolAction*) (/home/ubuntu2404/build-196067-assert/bin/clang-check+0xceae19)
#26 0x0000612f2e81b405 main (/home/ubuntu2404/build-196067-assert/bin/clang-check+0x385405)
#27 0x00007a0c3fe2a1ca __libc_start_call_main ./csu/../sysdeps/nptl/libc_start_call_main.h:74:3
#28 0x00007a0c3fe2a28b call_init ./csu/../csu/libc-start.c:128:20
#29 0x00007a0c3fe2a28b __libc_start_main ./csu/../csu/libc-start.c:347:5
#30 0x0000612f2e895045 _start (/home/ubuntu2404/build-196067-assert/bin/clang-check+0x3ff045)
Aborted (core dumped)
```

Start at buildTrailingReturn in clang/lib/Tooling/Syntax/BuildTree.cpp around line 1633, then reproduce the failure with the provided C++ input and clang-check --syntax-tree-dump command. Trace why the trailing-return arrow is not the expected token. Done means the syntax-tree dump completes without triggering the assertion for this input.

Written by the indexing model from the issue text.