core: apply protobuf patch to prevent duplicate symbols (#618)

Fixes #617, which resulted in duplicate symbols from protobuf being present in the final Envoy Mobile binary.

The [root cause](bazelbuild/bazel#10484) is being [patched in Bazel](bazelbuild/bazel#10493). In the meantime, we can revert these two commits in protobuf ([first](protocolbuffers/protobuf@7b28278), [second](protocolbuffers/protobuf@a03d332)) and apply the diff as a patch until we're able to update Bazel with the fix. More context on the protobuf issue is available [here](protocolbuffers/protobuf#7046).

Notes:
- This should be reverted after updating Bazel with the fix
- The version of protobuf specified in the `http_archive` should be in lockstep with upstream Envoy's version
- Upstream Envoy's `@envoy//bazel:protobuf.patch` patch is also included here

Signed-off-by: Michael Rebello <me@michaelrebello.com>

WORKSPACE

@@ -1,5 +1,20 @@
 load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive", "http_file", "http_jar")
 
+# Patch protobuf to prevent duplicate symbols: https://github.com/lyft/envoy-mobile/issues/617
+# More details: https://github.com/protocolbuffers/protobuf/issues/7046
+# TODO: Remove after https://github.com/bazelbuild/bazel/pull/10493 is merged to Bazel
+# Reverts:
+# - https://github.com/protocolbuffers/protobuf/commit/7b28278c7d4f4175e70aef2f89d304696eb85ae3
+# - https://github.com/protocolbuffers/protobuf/commit/a03d332aca5d33c5d4b2cd25037c9e37d57eff02
+http_archive(
+    name = "com_google_protobuf",
+    patch_args = ["-p1"],
+    patches = ["@envoy//bazel:protobuf.patch", "//bazel:protobuf.patch"],
+    sha256 = "d7cfd31620a352b2ee8c1ed883222a0d77e44346643458e062e86b1d069ace3e",
+    strip_prefix = "protobuf-3.10.1",
+    urls = ["https://github.com/protocolbuffers/protobuf/releases/download/v3.10.1/protobuf-all-3.10.1.tar.gz"],
+)
+
 # Patch upstream Abseil to prevent Foundation dependency from leaking into Android builds.
 # Workaround for https://github.com/abseil/abseil-cpp/issues/326.
 # TODO: Should be removed in https://github.com/lyft/envoy-mobile/issues/136 once rules_android

bazel/protobuf.patch

@@ -0,0 +1,93 @@
+diff --git a/BUILD b/BUILD
+index efc3d8e7f..425eb15d5 100644
+--- a/BUILD
++++ b/BUILD
+@@ -247,36 +247,38 @@ cc_library(
+ # Map of all well known protos.
+ # name => (include path, imports)
+ WELL_KNOWN_PROTO_MAP = {
+-    "any": ("src/google/protobuf/any.proto", []),
++    "any": ("google/protobuf/any.proto", []),
+     "api": (
+-        "src/google/protobuf/api.proto",
++        "google/protobuf/api.proto",
+         [
+             "source_context",
+             "type",
+         ],
+     ),
+     "compiler_plugin": (
+-        "src/google/protobuf/compiler/plugin.proto",
++        "google/protobuf/compiler/plugin.proto",
+         ["descriptor"],
+     ),
+-    "descriptor": ("src/google/protobuf/descriptor.proto", []),
+-    "duration": ("src/google/protobuf/duration.proto", []),
+-    "empty": ("src/google/protobuf/empty.proto", []),
+-    "field_mask": ("src/google/protobuf/field_mask.proto", []),
+-    "source_context": ("src/google/protobuf/source_context.proto", []),
+-    "struct": ("src/google/protobuf/struct.proto", []),
+-    "timestamp": ("src/google/protobuf/timestamp.proto", []),
++    "descriptor": ("google/protobuf/descriptor.proto", []),
++    "duration": ("google/protobuf/duration.proto", []),
++    "empty": ("google/protobuf/empty.proto", []),
++    "field_mask": ("google/protobuf/field_mask.proto", []),
++    "source_context": ("google/protobuf/source_context.proto", []),
++    "struct": ("google/protobuf/struct.proto", []),
++    "timestamp": ("google/protobuf/timestamp.proto", []),
+     "type": (
+-        "src/google/protobuf/type.proto",
++        "google/protobuf/type.proto",
+         [
+             "any",
+             "source_context",
+         ],
+     ),
+-    "wrappers": ("src/google/protobuf/wrappers.proto", []),
++    "wrappers": ("google/protobuf/wrappers.proto", []),
+ }
+
+-WELL_KNOWN_PROTOS = [value[0] for value in WELL_KNOWN_PROTO_MAP.values()]
++RELATIVE_WELL_KNOWN_PROTOS = [proto[1][0] for proto in WELL_KNOWN_PROTO_MAP.items()]
++
++WELL_KNOWN_PROTOS = ["src/" + s for s in RELATIVE_WELL_KNOWN_PROTOS]
+
+ filegroup(
+     name = "well_known_protos",
+@@ -306,10 +308,17 @@ cc_proto_library(
+ # )
+ ################################################################################
+
++internal_copied_filegroup(
++    name = "_internal_wkt_protos",
++    srcs = WELL_KNOWN_PROTOS,
++    dest = "",
++    strip_prefix = "src",
++    visibility = ["//visibility:private"],
++)
++
+ [proto_library(
+     name = proto[0] + "_proto",
+     srcs = [proto[1][0]],
+-    strip_import_prefix = "src",
+     visibility = ["//visibility:public"],
+     deps = [dep + "_proto" for dep in proto[1][1]],
+ ) for proto in WELL_KNOWN_PROTO_MAP.items()]
+@@ -869,7 +878,7 @@ internal_copied_filegroup(
+
+ # TODO(dzc): Remove this once py_proto_library can have labels in srcs, in
+ # which case we can simply add :protos_python in srcs.
+-COPIED_WELL_KNOWN_PROTOS = ["python/" + s[4:] for s in WELL_KNOWN_PROTOS]
++COPIED_WELL_KNOWN_PROTOS = ["python/" + s for s in RELATIVE_WELL_KNOWN_PROTOS]
+
+ py_proto_library(
+     name = "protobuf_python",
+@@ -988,7 +997,7 @@ cc_library(
+
+ proto_lang_toolchain(
+     name = "cc_toolchain",
+-    blacklisted_protos = [proto + "_proto" for proto in WELL_KNOWN_PROTO_MAP.keys()],
++    blacklisted_protos = [":_internal_wkt_protos_genrule"],
+     command_line = "--cpp_out=$(OUT)",
+     runtime = ":protobuf",
+     visibility = ["//visibility:public"],