[SourceKit] Enable PrettyStackTrace printing (#17205)

In particular, this will result in PrettyStackTrace messages being
included in crash logs when SourceKit crashes on Apple platforms.

Author: jrose-apple

tools/SourceKit/tools/sourcekitd/lib/API/Requests.cpp

@@ -36,6 +36,7 @@
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/Support/MemoryBuffer.h"
 #include "llvm/Support/Path.h"
+#include "llvm/Support/PrettyStackTrace.h"
 #include "llvm/Support/raw_ostream.h"
 #include <mutex>
 
@@ -91,6 +92,7 @@ static void onDocumentUpdateNotification(StringRef DocumentName) {
 static SourceKit::Context *GlobalCtx = nullptr;
 
 void sourcekitd::initialize() {
+  llvm::EnablePrettyStackTrace();
   GlobalCtx = new SourceKit::Context(sourcekitd::getRuntimeLibPath(),
                                      SourceKit::createSwiftLangSupport);
   GlobalCtx->getNotificationCenter().addDocumentUpdateNotificationReceiver(