Parser: install LLVM stack-trace signal handler in main

Install `llvm::sys::PrintStackTraceOnErrorSignal` at the top of `main()`
so a `SIGSEGV` / Windows SEH `STATUS_ACCESS_VIOLATION` from inside libclang
prints a backtrace to stderr instead of silently dying. Diagnostic-only —
no behavior change on the happy path.

With `RelWithDebInfo` builds (already the default per
`install_mrbind_windows_msys2.bat`), mrbind frames carry DWARF source
locations. libclang-cpp / libLLVM frames show function names only,
because msys2 strips DLL debug info.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: Fedr

src/parser/main.cpp

@@ -42,6 +42,8 @@
 #include <clang/Tooling/CommonOptionsParser.h>
 #include <clang/Tooling/Tooling.h>
 #include <llvm/Support/CommandLine.h>
+#include <llvm/Support/PrettyStackTrace.h>
+#include <llvm/Support/Signals.h>
 #include "post_include_clang.h"
 
 #include <array>
@@ -3470,6 +3472,13 @@ namespace mrbind
 
 int main(int raw_argc, char **raw_argv)
 {
+    // Print a stack trace to stderr on SIGSEGV / SEH access violations.
+    // RelWithDebInfo builds keep DWARF symbols in mrbind.exe, so the mrbind
+    // frames in the trace are line-numbered. libclang-cpp.dll frames will
+    // only show function names (msys2 strips DLL debug info).
+    llvm::sys::PrintStackTraceOnErrorSignal(raw_argv[0]);
+    llvm::PrettyStackTraceProgram pretty_stack(raw_argc, raw_argv);
+
     mrbind::SetErrorHandlers();
 
     std::string dump_command_to_file;