[Chromecast] Include all stdlibc++/libgcc symbols in cast_shell.

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.
+
+assert(is_chromecast)
+
+config("static_config") {
+  ldflags = [
+    # We want to statically link libstdc++/libgcc.
+    "-static-libstdc++",
+    "-static-libgcc",
+  ]
+}
+
+config("executable_config") {
+  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",
+
+    "-Wl,--whole-archive",
+    "-l:libstdc++.a",
+    "-l:libgcc.a",
+    "-Wl,--no-whole-archive",
+  ]
+
+  configs = [ ":static_config" ]

[bcf, 2015/12/02 02:37:23]

@wzhong, we talked about how this may not be necessary for executables because
of the -l:libstdc++.a, but it seems that it is necessary otherwise cast_shell
will have a dynamic dependency on libstdc++.so.

[wzhong, 2015/12/02 02:42:52]

Please add this to comment as this is not obvious and seems redundant at first
glance. 

[bcf, 2015/12/02 03:20:23]

Done.

+}
+
+config("shlib_config") {
+  configs = [ ":static_config" ]
+}