Add in build files.

vendor/github.com/Azure/go-ansiterm/BUILD

@@ -0,0 +1,43 @@
+package(default_visibility = ["//visibility:public"])
+
+licenses(["notice"])
+
+load(
+    "@io_bazel_rules_go//go:def.bzl",
+    "go_library",
+)
+
+go_library(
+    name = "go_default_library",
+    srcs = [
+        "constants.go",
+        "context.go",
+        "csi_entry_state.go",
+        "csi_param_state.go",
+        "escape_intermediate_state.go",
+        "escape_state.go",
+        "event_handler.go",
+        "ground_state.go",
+        "osc_string_state.go",
+        "parser.go",
+        "parser_action_helpers.go",
+        "parser_actions.go",
+        "states.go",
+        "utilities.go",
+    ],
+    tags = ["automanaged"],
+    deps = ["//vendor/github.com/Sirupsen/logrus:go_default_library"],
+)
+
+filegroup(
+    name = "package-srcs",
+    srcs = glob(["**"]),
+    tags = ["automanaged"],
+    visibility = ["//visibility:private"],
+)
+
+filegroup(
+    name = "all-srcs",
+    srcs = [":package-srcs"],
+    tags = ["automanaged"],
+)