[gn build] Port 2f0d755

Author: llvmgnsyncbot

llvm/utils/gn/secondary/llvm/unittests/Object/BUILD.gn

@@ -15,5 +15,6 @@ unittest("ObjectTests") {
     "ObjectFileTest.cpp",
     "SymbolSizeTest.cpp",
     "SymbolicFileTest.cpp",
+    "XCOFFObjectFileTest.cpp",
   ]
 }