[gn build] (manually) port 0c2b43ab8c (X86MCTests)

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

@@ -93,6 +93,7 @@ group("unittests") {
   }
   if (llvm_build_X86) {
     deps += [
+      "MC/X86:X86MCTests",
       "Target/X86:X86Tests",
       "tools/llvm-exegesis/X86:LLVMExegesisX86Tests",
     ]

llvm/utils/gn/secondary/llvm/unittests/MC/X86/BUILD.gn

@@ -0,0 +1,12 @@
+import("//llvm/utils/unittest/unittest.gni")
+
+unittest("X86MCTests") {
+  deps = [
+    "//llvm/lib/MC",
+    "//llvm/lib/MC/MCDisassembler",
+    "//llvm/lib/Target",
+    "//llvm/lib/Target/X86/MCTargetDesc",
+    "//llvm/lib/Target/X86/Disassembler",
+  ]
+  sources = [ "X86MCDisassemblerTest.cpp" ]
+}