Include ARM64 in “select” calls. (#2825)

These files are architecture-independent, so this works on ARM-64 without
further changes.

tests/legacy/cgo_select/BUILD.bazel

diff --git a/tests/legacy/cgo_select/BUILD.bazel b/tests/legacy/cgo_select/BUILD.bazel
index 2dffa51..5dd9108 100644
--- a/tests/legacy/cgo_select/BUILD.bazel
+++ b/tests/legacy/cgo_select/BUILD.bazel
@@ -7,6 +7,9 @@
         "@io_bazel_rules_go//go/platform:darwin_amd64": [
             "cgo_darwin.go",
         ],
+        "@io_bazel_rules_go//go/platform:darwin_arm64": [
+            "cgo_darwin.go",
+        ],
         "@io_bazel_rules_go//go/platform:linux_amd64": [
             "cgo_linux.go",
         ],
@@ -18,6 +21,9 @@
         "@io_bazel_rules_go//go/platform:darwin_amd64": [
             ":darwin_lib",
         ],
+        "@io_bazel_rules_go//go/platform:darwin_arm64": [
+            ":darwin_lib",
+        ],
         "@io_bazel_rules_go//go/platform:linux_amd64": [
             ":linux_lib",
         ],