[gn build] Fix CodeGenTests

[aeubanks]

Summary

Missing dependency required by https://reviews.llvm.org/D67687.

Fixes
lld-link: error: undefined symbol: public: __cdecl llvm::PipelineTuningOptions::PipelineTuningOptions(void)

referenced by C:\src\llvm-project\llvm\unittests\CodeGen\PassManagerTest.cpp:215

obj/llvm/unittests/CodeGen/CodeGenTests.PassManagerTest.obj:(private: virtual void __cdecl `anonymous namespace'::PassManagerTest_Basic_Test::TestBody(void))

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

 import("//llvm/utils/unittest/unittest.gni")
 
 unittest("CodeGenTests") {
   deps = [
     "//llvm/lib/Analysis",
     "//llvm/lib/AsmParser",
     "//llvm/lib/CodeGen",
     "//llvm/lib/CodeGen/AsmPrinter",
     "//llvm/lib/CodeGen/SelectionDAG",
     "//llvm/lib/IR",
     "//llvm/lib/MC",
+    "//llvm/lib/Passes",
     "//llvm/lib/Support",
     "//llvm/lib/Target",
     "//llvm/lib/Target:TargetsToBuild",
   ]
   sources = [
     "AArch64SelectionDAGTest.cpp",
     "DIEHashTest.cpp",
     "LexicalScopesTest.cpp",