[clangd] Use #if CLANGD_BUILD_XPC because it may be defined as 0

llvm-svn: 358094

clang-tools-extra/clangd/Transport.h

@@ -85,7 +85,7 @@ newJSONTransport(std::FILE *In, llvm::raw_ostream &Out,
                  llvm::raw_ostream *InMirror, bool Pretty,
                  JSONStreamStyle = JSONStreamStyle::Standard);
 
-#ifdef CLANGD_BUILD_XPC
+#if CLANGD_BUILD_XPC
 // Returns a Transport for macOS based on XPC.
 // Clangd with this transport is meant to be run as bundled XPC service.
 std::unique_ptr<Transport> newXPCTransport();