Split protoc into library and executable.

third_party/protobuf/BUILD.gn

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 config("protobuf_config") {
   include_dirs = [ "src" ]
   defines = [
     "GOOGLE_PROTOBUF_NO_RTTI",
     "GOOGLE_PROTOBUF_NO_STATIC_INITIALIZER",
   ]
@@ skipping 311 matching lines @@
 
     # TODO(jschuh): crbug.com/167187 fix size_t to int truncations.
     "//build/config/compiler:no_size_t_to_int_warning",
   ]
 
   cflags = protobuf_lite_cflags
 }
 
 # Only compile the compiler for the host architecture.
 if (current_toolchain == host_toolchain) {
-  executable("protoc") {
+  source_set("protoc_lib") {
     sources = [
       "src/google/protobuf/compiler/code_generator.cc",
       "src/google/protobuf/compiler/code_generator.h",
       "src/google/protobuf/compiler/command_line_interface.cc",
       "src/google/protobuf/compiler/command_line_interface.h",
       "src/google/protobuf/compiler/cpp/cpp_enum.cc",
       "src/google/protobuf/compiler/cpp/cpp_enum.h",
       "src/google/protobuf/compiler/cpp/cpp_enum_field.cc",
       "src/google/protobuf/compiler/cpp/cpp_enum_field.h",
       "src/google/protobuf/compiler/cpp/cpp_extension.cc",
@@ skipping 126 matching lines @@
       "src/google/protobuf/compiler/javanano/javanano_map_field.cc",
       "src/google/protobuf/compiler/javanano/javanano_map_field.h",
       "src/google/protobuf/compiler/javanano/javanano_message.cc",
       "src/google/protobuf/compiler/javanano/javanano_message.h",
       "src/google/protobuf/compiler/javanano/javanano_message_field.cc",
       "src/google/protobuf/compiler/javanano/javanano_message_field.h",
       "src/google/protobuf/compiler/javanano/javanano_primitive_field.cc",
       "src/google/protobuf/compiler/javanano/javanano_primitive_field.h",
       "src/google/protobuf/compiler/js/js_generator.cc",
       "src/google/protobuf/compiler/js/js_generator.h",
-      "src/google/protobuf/compiler/main.cc",
       "src/google/protobuf/compiler/objectivec/objectivec_enum.cc",
       "src/google/protobuf/compiler/objectivec/objectivec_enum.h",
       "src/google/protobuf/compiler/objectivec/objectivec_enum_field.cc",
       "src/google/protobuf/compiler/objectivec/objectivec_enum_field.h",
       "src/google/protobuf/compiler/objectivec/objectivec_extension.cc",
       "src/google/protobuf/compiler/objectivec/objectivec_extension.h",
       "src/google/protobuf/compiler/objectivec/objectivec_field.cc",
       "src/google/protobuf/compiler/objectivec/objectivec_field.h",
       "src/google/protobuf/compiler/objectivec/objectivec_file.cc",
       "src/google/protobuf/compiler/objectivec/objectivec_file.h",
@@ skipping 31 matching lines @@
 
       # Must be after no_chromium_code for warning flags to be ordered
       # correctly.
       ":protobuf_warnings",
     ]
     if (is_win) {
       # This is defined internally, don't warn on duplicate.
       configs -= [ "//build/config/win:lean_and_mean" ]
     }
 
+    public_configs = [ ":protobuf_config" ]
+
     cflags = protobuf_lite_cflags
 
     deps = [
       ":protobuf_full",
-      "//build/config/sanitizers:deps",
+    ]
+  }
+
+  executable("protoc") {
+    sources = [
+      "src/google/protobuf/compiler/main.cc",
+    ]
+
+    configs -= [ "//build/config/compiler:chromium_code" ]
+    configs += ["//build/config/compiler:no_chromium_code"]
+
+    cflags = protobuf_lite_cflags
+
+    deps = [
+      ":protobuf_full",

[Peter Kasting, 2016/04/28 00:29:36]

If this needs to depend on protobuf_full because anything that depends on
protoc_lib needs to depend on that, there's some syntax you should use instead
in the protoc_lib definition that basically says "treat protobuf_full as a
dependency of anything that depends on me".  I don't remember what this syntax
is, though.

[xyzzyz, 2016/04/28 20:00:31]

I think it's "public_deps". Setting this for protoc_lib.

+      ":protoc_lib",
 
       # Default manifest on Windows (a no-op elsewhere).
       "//build/win:default_exe_manifest",
     ]
-    deps += [ "//build/config/sanitizers:deps" ]
   }
 }
 
 google_python_dir = "$root_out_dir/pyproto/google"
 
 copy("copy_google") {
   sources = [
     "__init__.py",
   ]
   outputs = [
@@ skipping 66 matching lines @@
     ":copy_google_protobuf_internal",
     ":copy_six",
   ]
 
   # Targets that depend on this should depend on the copied data files.
   data = get_target_outputs(":copy_google")
   data += get_target_outputs(":copy_six")
   data += get_target_outputs(":copy_google_protobuf")
   data += get_target_outputs(":copy_google_protobuf_internal")
 }