Add missing isPCHFilenameExtension declaration

Author: MaxDesiatov

lib/ClangImporter/ClangImporter.cpp

@@ -513,6 +513,19 @@ getWasiLibcModuleMapPath(SearchPathOptions& Opts, llvm::Triple triple,
   return None;
 }
 
+static bool clangSupportsPragmaAttributeWithSwiftAttr() {
+  clang::AttributeCommonInfo swiftAttrInfo(clang::SourceRange(),
+     clang::AttributeCommonInfo::AT_SwiftAttr,
+     clang::AttributeCommonInfo::AS_GNU);
+  auto swiftAttrParsedInfo = clang::ParsedAttrInfo::get(swiftAttrInfo);
+  return swiftAttrParsedInfo.IsSupportedByPragmaAttribute;
+}
+
+static inline bool isPCHFilenameExtension(StringRef path) {
+  return llvm::sys::path::extension(path)
+    .endswith(file_types::getExtension(file_types::TY_PCH));
+}
+
 void
 importer::getNormalInvocationArguments(
     std::vector<std::string> &invocationArgStrs,