fix: disable Java toolchain which is causing C++ compiles

Author: alexeagle

examples/BUILD.bazel

@@ -15,10 +15,11 @@ py_proto_library(
     deps = [":foo_proto"],
 )
 
-java_proto_library(
-    name = "foo_java_proto",
-    deps = [":foo_proto"],
-)
+# See comment in examples/tools/toolchains/BUILD.bazel
+# java_proto_library(
+#     name = "foo_java_proto",
+#     deps = [":foo_proto"],
+# )
 
 go_proto_library(
     name = "foo_go_proto",

examples/tools/toolchains/BUILD.bazel

@@ -19,13 +19,16 @@ proto_lang_toolchain(
 )
 
 # Same as above, but for Java
-proto_lang_toolchain(
-    name = "protoc_java_toolchain",
-    command_line = "--java_out=%s",
-    progress_message = "Generating Java proto_library %{label}",
-    runtime = "@protobuf-java//jar",
-    toolchain_type = "@rules_java//java/proto:toolchain_type",
-)
+# Broken by https://github.com/protocolbuffers/protobuf/pull/19679
+# which causes building C++ code from source.
+# TODO: re-enable once protobuf honors the toolchain
+# proto_lang_toolchain(
+#     name = "protoc_java_toolchain",
+#     command_line = "--java_out=%s",
+#     progress_message = "Generating Java proto_library %{label}",
+#     runtime = "@protobuf-java//jar",
+#     toolchain_type = "@rules_java//java/proto:toolchain_type",
+# )
 
 ################
 # Setup a non-functional C++ toolchain, so we're assured that no C++ compilation