Collapse :protobuf_objc and :objectivec targets.

Not sure the history for why there were two objc_library targets, but
given the one has an issue about not working, merge them into a single
target and an alias.

- Use the alias for :objectivec since that naming doesn't seem to follow
  the other targets *_library targets here.
- Update :protobuf_objc to be use for the working target and just inline
  the sources/headers lists so there is less indirection in the file.

Fixes #5284

BUILD

@@ -196,14 +196,6 @@ cc_library(
     visibility = ["//visibility:public"],
 )
 
-objc_library(
-    name = "protobuf_objc",
-    hdrs = ["objectivec/GPBProtocolBuffers.h"],
-    includes = ["objectivec"],
-    non_arc_srcs = ["objectivec/GPBProtocolBuffers.m"],
-    visibility = ["//visibility:public"],
-)
-
 # Map of all well known protos.
 # name => (include path, imports)
 WELL_KNOWN_PROTO_MAP = {
@@ -861,87 +853,88 @@ proto_lang_toolchain(
     visibility = ["//visibility:public"],
 )
 
-OBJC_HDRS = [
-    "objectivec/GPBArray.h",
-    "objectivec/GPBBootstrap.h",
-    "objectivec/GPBCodedInputStream.h",
-    "objectivec/GPBCodedOutputStream.h",
-    "objectivec/GPBDescriptor.h",
-    "objectivec/GPBDictionary.h",
-    "objectivec/GPBExtensionInternals.h",
-    "objectivec/GPBExtensionRegistry.h",
-    "objectivec/GPBMessage.h",
-    "objectivec/GPBProtocolBuffers.h",
-    "objectivec/GPBProtocolBuffers_RuntimeSupport.h",
-    "objectivec/GPBRootObject.h",
-    "objectivec/GPBRuntimeTypes.h",
-    "objectivec/GPBUnknownField.h",
-    "objectivec/GPBUnknownFieldSet.h",
-    "objectivec/GPBUtilities.h",
-    "objectivec/GPBWellKnownTypes.h",
-    "objectivec/GPBWireFormat.h",
-    "objectivec/google/protobuf/Any.pbobjc.h",
-    "objectivec/google/protobuf/Api.pbobjc.h",
-    "objectivec/google/protobuf/Duration.pbobjc.h",
-    "objectivec/google/protobuf/Empty.pbobjc.h",
-    "objectivec/google/protobuf/FieldMask.pbobjc.h",
-    "objectivec/google/protobuf/SourceContext.pbobjc.h",
-    "objectivec/google/protobuf/Struct.pbobjc.h",
-    "objectivec/google/protobuf/Timestamp.pbobjc.h",
-    "objectivec/google/protobuf/Type.pbobjc.h",
-    "objectivec/google/protobuf/Wrappers.pbobjc.h",
-]
-
-OBJC_PRIVATE_HDRS = [
-    "objectivec/GPBArray_PackagePrivate.h",
-    "objectivec/GPBCodedInputStream_PackagePrivate.h",
-    "objectivec/GPBCodedOutputStream_PackagePrivate.h",
-    "objectivec/GPBDescriptor_PackagePrivate.h",
-    "objectivec/GPBDictionary_PackagePrivate.h",
-    "objectivec/GPBMessage_PackagePrivate.h",
-    "objectivec/GPBRootObject_PackagePrivate.h",
-    "objectivec/GPBUnknownFieldSet_PackagePrivate.h",
-    "objectivec/GPBUnknownField_PackagePrivate.h",
-    "objectivec/GPBUtilities_PackagePrivate.h",
-]
-
-OBJC_SRCS = [
-    "objectivec/GPBArray.m",
-    "objectivec/GPBCodedInputStream.m",
-    "objectivec/GPBCodedOutputStream.m",
-    "objectivec/GPBDescriptor.m",
-    "objectivec/GPBDictionary.m",
-    "objectivec/GPBExtensionInternals.m",
-    "objectivec/GPBExtensionRegistry.m",
-    "objectivec/GPBMessage.m",
-    "objectivec/GPBRootObject.m",
-    "objectivec/GPBUnknownField.m",
-    "objectivec/GPBUnknownFieldSet.m",
-    "objectivec/GPBUtilities.m",
-    "objectivec/GPBWellKnownTypes.m",
-    "objectivec/GPBWireFormat.m",
-    "objectivec/google/protobuf/Any.pbobjc.m",
-    "objectivec/google/protobuf/Api.pbobjc.m",
-    "objectivec/google/protobuf/Duration.pbobjc.m",
-    "objectivec/google/protobuf/Empty.pbobjc.m",
-    "objectivec/google/protobuf/FieldMask.pbobjc.m",
-    "objectivec/google/protobuf/SourceContext.pbobjc.m",
-    "objectivec/google/protobuf/Struct.pbobjc.m",
-    "objectivec/google/protobuf/Timestamp.pbobjc.m",
-    "objectivec/google/protobuf/Type.pbobjc.m",
-    "objectivec/google/protobuf/Wrappers.pbobjc.m",
-]
+alias(
+    name = "objectivec",
+    actual = ":protobuf_objc",
+    visibility = ["//visibility:public"],
+)
 
 objc_library(
-    name = "objectivec",
-    hdrs = OBJC_HDRS + OBJC_PRIVATE_HDRS,
+    name = "protobuf_objc",
+    hdrs = [
+        "objectivec/GPBArray.h",
+        "objectivec/GPBBootstrap.h",
+        "objectivec/GPBCodedInputStream.h",
+        "objectivec/GPBCodedOutputStream.h",
+        "objectivec/GPBDescriptor.h",
+        "objectivec/GPBDictionary.h",
+        "objectivec/GPBExtensionInternals.h",
+        "objectivec/GPBExtensionRegistry.h",
+        "objectivec/GPBMessage.h",
+        "objectivec/GPBProtocolBuffers.h",
+        "objectivec/GPBProtocolBuffers_RuntimeSupport.h",
+        "objectivec/GPBRootObject.h",
+        "objectivec/GPBRuntimeTypes.h",
+        "objectivec/GPBUnknownField.h",
+        "objectivec/GPBUnknownFieldSet.h",
+        "objectivec/GPBUtilities.h",
+        "objectivec/GPBWellKnownTypes.h",
+        "objectivec/GPBWireFormat.h",
+        "objectivec/google/protobuf/Any.pbobjc.h",
+        "objectivec/google/protobuf/Api.pbobjc.h",
+        "objectivec/google/protobuf/Duration.pbobjc.h",
+        "objectivec/google/protobuf/Empty.pbobjc.h",
+        "objectivec/google/protobuf/FieldMask.pbobjc.h",
+        "objectivec/google/protobuf/SourceContext.pbobjc.h",
+        "objectivec/google/protobuf/Struct.pbobjc.h",
+        "objectivec/google/protobuf/Timestamp.pbobjc.h",
+        "objectivec/google/protobuf/Type.pbobjc.h",
+        "objectivec/google/protobuf/Wrappers.pbobjc.h",
+        # Package private headers, but exposed because the generated sources
+        # need to use them.
+        "objectivec/GPBArray_PackagePrivate.h",
+        "objectivec/GPBCodedInputStream_PackagePrivate.h",
+        "objectivec/GPBCodedOutputStream_PackagePrivate.h",
+        "objectivec/GPBDescriptor_PackagePrivate.h",
+        "objectivec/GPBDictionary_PackagePrivate.h",
+        "objectivec/GPBMessage_PackagePrivate.h",
+        "objectivec/GPBRootObject_PackagePrivate.h",
+        "objectivec/GPBUnknownFieldSet_PackagePrivate.h",
+        "objectivec/GPBUnknownField_PackagePrivate.h",
+        "objectivec/GPBUtilities_PackagePrivate.h",
+    ],
     copts = [
         "-Wno-vla",
     ],
     includes = [
         "objectivec",
     ],
-    non_arc_srcs = OBJC_SRCS,
+    non_arc_srcs = [
+        "objectivec/GPBArray.m",
+        "objectivec/GPBCodedInputStream.m",
+        "objectivec/GPBCodedOutputStream.m",
+        "objectivec/GPBDescriptor.m",
+        "objectivec/GPBDictionary.m",
+        "objectivec/GPBExtensionInternals.m",
+        "objectivec/GPBExtensionRegistry.m",
+        "objectivec/GPBMessage.m",
+        "objectivec/GPBRootObject.m",
+        "objectivec/GPBUnknownField.m",
+        "objectivec/GPBUnknownFieldSet.m",
+        "objectivec/GPBUtilities.m",
+        "objectivec/GPBWellKnownTypes.m",
+        "objectivec/GPBWireFormat.m",
+        "objectivec/google/protobuf/Any.pbobjc.m",
+        "objectivec/google/protobuf/Api.pbobjc.m",
+        "objectivec/google/protobuf/Duration.pbobjc.m",
+        "objectivec/google/protobuf/Empty.pbobjc.m",
+        "objectivec/google/protobuf/FieldMask.pbobjc.m",
+        "objectivec/google/protobuf/SourceContext.pbobjc.m",
+        "objectivec/google/protobuf/Struct.pbobjc.m",
+        "objectivec/google/protobuf/Timestamp.pbobjc.m",
+        "objectivec/google/protobuf/Type.pbobjc.m",
+        "objectivec/google/protobuf/Wrappers.pbobjc.m",
+    ],
     visibility = ["//visibility:public"],
 )