[gn build] Manually port 8566cd6

Author: aeubanks

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

@@ -7,6 +7,7 @@ unittest("MIRTests") {
     "//llvm/lib/FileCheck",
     "//llvm/lib/IR",
     "//llvm/lib/MC",
+    "//llvm/lib/Passes",
     "//llvm/lib/Support",
     "//llvm/lib/Target",
     "//llvm/lib/Target:TargetsToBuild",