feat: re-enable Java example of using pre-built protoc

Author: alexeagle

examples/BUILD.bazel

@@ -17,13 +17,10 @@ proto_library(
 #     deps = [":foo_proto"],
 # )
 
-# Broken by https://github.com/protocolbuffers/protobuf/pull/19679
-# which causes building C++ code from source.
-# TODO: re-enable once protobuf honors the toolchain
-# java_proto_library(
-#     name = "foo_java_proto",
-#     deps = [":foo_proto"],
-# )
+java_proto_library(
+    name = "foo_java_proto",
+    deps = [":foo_proto"],
+)
 
 go_proto_library(
     name = "foo_go_proto",

examples/java/BUILD

@@ -1,10 +1,9 @@
-# See comment in examples/BUILD.bazel
-# java_binary(
-#     name = "java",
-#     srcs = ["Main.java"],
-#     main_class = "Main",
-#     deps = [
-#         "//:foo_java_proto",
-#         "@protobuf-java//jar",
-#     ],
-# )
+java_binary(
+    name = "java",
+    srcs = ["Main.java"],
+    main_class = "Main",
+    deps = [
+        "//:foo_java_proto",
+        "@protobuf-java//jar",
+    ],
+)