[gn build] Port c5b417c

Author: llvmgnsyncbot

llvm/utils/gn/secondary/llvm/lib/SandboxIR/BUILD.gn

@@ -13,5 +13,6 @@ static_library("SandboxIR") {
     "SandboxIR.cpp",
     "Tracker.cpp",
     "Type.cpp",
+    "Value.cpp",
   ]
 }