Swift: lock built swiftmodule traps in main

This should cover `-merge-modules` mode.

Dumping of the configuration to the target files was moved to a
separate pair of header/source files, as now it is also done in
`SwiftOutputRewrite.cpp`.

swift/extractor/TargetTrapFile.cpp

@@ -0,0 +1,23 @@
+#include "swift/extractor/TargetTrapFile.h"
+#include <iomanip>
+namespace codeql {
+std::optional<TargetFile> createTargetTrapFile(const SwiftExtractorConfiguration& configuration,
+                                               std::string_view target) {
+  std::string trap{target};
+  trap += ".trap";
+  auto ret = TargetFile::create(trap, configuration.trapDir, configuration.getTempTrapDir());
+  if (ret) {
+    *ret << "/* extractor-args:\n";
+    for (const auto& opt : configuration.frontendOptions) {
+      *ret << "  " << std::quoted(opt) << " \\\n";
+    }
+    *ret << "\n*/\n"
+            "/* swift-frontend-args:\n";
+    for (const auto& opt : configuration.patchedFrontendOptions) {
+      *ret << "  " << std::quoted(opt) << " \\\n";
+    }
+    *ret << "\n*/\n";
+  }
+  return ret;
+}
+}  // namespace codeql