[gn build] Port e22b07e766e4

Author: llvmgnsyncbot

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

@@ -10,6 +10,7 @@ static_library("SandboxIR") {
     "BasicBlock.cpp",
     "Constant.cpp",
     "Context.cpp",
+    "Function.cpp",
     "Instruction.cpp",
     "Module.cpp",
     "Pass.cpp",