Move build/secondary/third_party/nss/BUILD.gn to build/confix/linux/nss/.

We haven't been DEPS'ing in third_party/nss for a long time, so having
the build file there is misleading. Since it uses pkg-config, put it
in build/config/linux, where most other pkg-config-using system dependencies
live.

TBR=stevenjb

Bug: none
Change-Id: Iaa32ba43898303a5072edb2b183beb89a220d78a
Reviewed-on: https://chromium-review.googlesource.com/1193965
Commit-Queue: Nico Weber <thakis@chromium.org>
Reviewed-by: Ryan Sleevi <rsleevi@chromium.org>
Reviewed-by: Thomas Anderson <thomasanderson@chromium.org>
Cr-Commit-Position: refs/heads/master@{#586775}

chromeos/BUILD.gn

@@ -16,7 +16,7 @@ declare_args() {
 }
 
 component("chromeos") {
-  configs += [ "//third_party/nss:system_nss_no_ssl_config" ]
+  configs += [ "//build/config/linux/nss:system_nss_no_ssl_config" ]
   public_deps = [
     "//dbus",
   ]
@@ -654,7 +654,7 @@ static_library("test_support_without_gmock") {
 test("chromeos_unittests") {
   configs += [
     "//build/config/linux/dbus",
-    "//third_party/nss:system_nss_no_ssl_config",
+    "//build/config/linux/nss:system_nss_no_ssl_config",
   ]
   deps = [
     ":attestation_proto",

crypto/BUILD.gn

@@ -217,6 +217,6 @@ group("platform") {
   # (use_nss_certs).
   if (use_nss_certs) {
     public_configs = [ ":platform_config" ]
-    public_configs += [ "//third_party/nss:system_nss_no_ssl_config" ]
+    public_configs += [ "//build/config/linux/nss:system_nss_no_ssl_config" ]
   }
 }