[Chromecast] Only include all libstdc++/libgcc symbols in executable as needed

build/config/chromecast/BUILD.gn

 # Copyright 2015 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.
 
 import("//build/config/chromecast_build.gni")
 
 assert(is_chromecast)
 
 config("static_config") {
   ldflags = [
@@ skipping 16 matching lines @@
   # This is explicitly disabled in Chrome for security reasons (see comments in
   # //build/config/gcc/BUILD.gn), but necessary on Chromecast so that OEM's may
   # override the default libraries shipped in the Cast receiver package.
   ldflags = [
     "-Wl,-rpath=/oem_cast_shlib",
     "-Wl,-rpath=\$ORIGIN/lib",
     "-Wl,-rpath=\$ORIGIN",
   ]
 }
 
-config("executable_config") {
-  configs = [ ":ldconfig" ]
-
+# whole archiving libgcc.a and libstdc++ is needed if dynamic share libs are

[bcf, 2016/08/29 23:26:15]

Super nit: Capitalize and use periods at end of sentences.

+# used, see b/25566835
+config("executable_whole_archive_config") {
   if (current_cpu == "arm") {
     ldflags = [
       # Export stdlibc++ and libgcc symbols to force shlibs to refer to these
       # symbols from the executable.
       "-Wl,--export-dynamic",
 
       "-lm",  # stdlibc++ requires math.h
 
       # In case we redefined stdlibc++ symbols (e.g. tc_malloc)
       "-Wl,--allow-multiple-definition",
 
+      # adding all symbols from libgcc and libstdc++
       "-Wl,--whole-archive",
       "-l:libstdc++.a",
       "-l:libgcc.a",
       "-Wl,--no-whole-archive",
     ]
+  }
+}
 
-    # Despite including libstdc++/libgcc archives, we still need to specify
-    # static linking for them in order to prevent the executable from having a
-    # dynamic dependency on them.
+config("executable_config") {
+  configs = [ ":ldconfig" ]
+
+  if (current_cpu == "arm") {
+    # static linking in order to prevent the executable from having a dynamic

[bcf, 2016/08/29 23:26:15]

"Statically link libstdc++ and libgcc to avoid having a dynamic dependency on
them."

[bcf, 2016/08/29 23:40:36]

Can you make this sentence more clear? By itself it doesn't make much sense
right now. Something like I said in the above comment would work.

[antz1, 2016/08/30 00:00:28]

Done.

+    # dependency on them.
     configs += [ ":static_config" ]
   }
 }
 
 config("shared_library_config") {
   configs = [ ":ldconfig" ]
   if (current_cpu == "arm") {
     configs += [ ":static_config" ]
   }
 }