Fix BUILD.gn.

TBR=yanggou@chromium.org

Review URL: https://codereview.chromium.org/488103002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@23232 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

BUILD.gn

@@ -511,6 +511,8 @@ source_set("v8_base") {
     "src/compiler/machine-operator-reducer.cc",
     "src/compiler/machine-operator-reducer.h",
     "src/compiler/machine-operator.h",
+    "src/compiler/machine-type.cc",
+    "src/compiler/machine-type.h",
     "src/compiler/node-aux-data-inl.h",
     "src/compiler/node-aux-data.h",
     "src/compiler/node-cache.cc",