Add Linux SDK to GN build.

I forgot to actually reference this config when I created it.

R=thakis@chromium.org
TBR=thakis

Review URL: https://codereview.chromium.org/155653002

git-svn-id: http://src.chromium.org/svn/trunk/src/build@249301 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

config/BUILDCONFIG.gn

@@ -336,6 +336,8 @@ native_compiler_configs = [
 ]
 if (is_win) {
   native_compiler_configs += [ "//build/config/win:sdk", ]
+} else if (is_linux) {
+  native_compiler_configs += [ "//build/config/linux:sdk", ]
 } else if (is_mac) {
   native_compiler_configs += [ "//build/config/mac:sdk", ]
 } else if (is_ios) {