Fix protoc dependency race.

According to Eureka team, using protobuf_lib_type=="target" without a
direct dependency on a protoc target causes flakiness in the build.
This introduces a new variable to represent the protoc host target,
with a default value for platforms like iOS where a prebuilt copy of
protoc is used.

Change-Id: I39c08bd76c6bc4a5291b0e19b2d22a9f3beb04d0

cdm/cdm.gyp

@@ -104,5 +104,9 @@
         'wvcdm_static',
       ],
     },
+    {
+      'target_name': 'dummy',
+      'type': 'none',
+    }
   ],
 }

platforms/global_config.gypi

@@ -26,6 +26,7 @@
     # 2) protobuf_lib_type == 'target'
     # Use an existing protobuf gyp target from your project.
     # Specify the protobuf gyp file and target in protobuf_lib.
+    # Specify the protoc gyp file and target in protoc_host_target (optional).
     # Specify the path to protoc in protoc_dir.
     #
     # 3) protobuf_lib_type == 'source'
@@ -35,6 +36,7 @@
     'protobuf_lib_type%': 'system',
     'protobuf_lib%': '-lprotobuf',
     'protoc_dir%': '/usr/bin',
+    'protoc_host_target%': 'dummy',
   }, # end variables
 
   'target_defaults': {

third_party/protoc.gypi

@@ -17,9 +17,11 @@
       # protobuf_lib is a gyp target.
       'dependencies': [
         '<(protobuf_lib)',
+        '<(protoc_host_target)',
       ],
       'export_dependent_settings': [
         '<(protobuf_lib)',
+        '<(protoc_host_target)',
       ],
     }],
     ['protobuf_lib_type=="source"', {