Remove the GN *sdk targets

build/config/posix/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/sysroot.gni")
+
+assert(is_posix)
+
+# This is included by reference in the //build/config/compiler:runtime_library
+# config that is applied to all targets. It is here to separate out the logic
+# that is Posix-only. Please see that target for advice on what should go in
+# :runtime_library vs. :compiler.
+config("runtime_library") {
+  if (!is_mac && sysroot != "") {
+    # Pass the sysroot to all C compiler variants, the assembler, and linker.
+    cflags = [ "--sysroot=" + sysroot ]
+    asmflags = cflags
+    ldflags = cflags
+
+    # Need to get some linker flags out of the sysroot.
+    ldflags += [ exec_script("sysroot_ld_path.py",
+                             [
+                               rebase_path("//build/linux/sysroot_ld_path.sh",
+                                           root_build_dir),
+                               sysroot,
+                             ],
+                             "value") ]
+  }
+}