Fix select with conditons on darwin.

Bazel is changing how @bazel_tools/conditions:darwin is implemented.
With old implementation based on flags, it was ok to have darwin and
darwin_x86_64 in a select. This was based on flag --cpu=darwin and
--cpu=dawin_x86_64.

New implementation is based on constraints, where "darwin" means OS (and
any CPU), while "darwin_x86_64" mean only specific CPU. As such they
cannot be used in the same select, because the selection would be
ambiguous.

toolchains/node/BUILD.bazel

@@ -78,7 +78,6 @@ alias(
     name = "toolchain",
     actual = select({
         "@bazel_tools//src/conditions:darwin": "@nodejs_darwin_amd64_config//:toolchain",
-        "@bazel_tools//src/conditions:darwin_x86_64": "@nodejs_darwin_amd64_config//:toolchain",
         "@bazel_tools//src/conditions:linux_aarch64": "@nodejs_linux_arm64_config//:toolchain",
         "@bazel_tools//src/conditions:linux_s390x": "@nodejs_linux_s390x_config//:toolchain",
         "@bazel_tools//src/conditions:linux_x86_64": "@nodejs_linux_amd64_config//:toolchain",
@@ -93,7 +92,6 @@ alias(
     name = "node_bin",
     actual = select({
         "@bazel_tools//src/conditions:darwin": "@nodejs_darwin_amd64//:node_bin",
-        "@bazel_tools//src/conditions:darwin_x86_64": "@nodejs_darwin_amd64//:node_bin",
         "@bazel_tools//src/conditions:linux_aarch64": "@nodejs_linux_arm64//:node_bin",
         "@bazel_tools//src/conditions:linux_s390x": "@nodejs_linux_s390x//:node_bin",
         "@bazel_tools//src/conditions:linux_x86_64": "@nodejs_linux_amd64//:node_bin",