Build nacl_helper_nonsfi with GN

sandbox/linux/BUILD.gn

Index: sandbox/linux/BUILD.gn
diff --git a/sandbox/linux/BUILD.gn b/sandbox/linux/BUILD.gn
index e734324e268651d4a638227c7871deef3f8606b5..01df2aa529a3198e23b38cee81a4a1984334d3d9 100644
--- a/sandbox/linux/BUILD.gn
+++ b/sandbox/linux/BUILD.gn
@@ -3,6 +3,7 @@
 # found in the LICENSE file.
 
 import("//build/config/features.gni")
+import("//build/config/nacl/config.gni")
 import("//testing/test.gni")
 
 declare_args() {
@@ -411,3 +412,44 @@ if (is_android) {
   #      'includes': [ '../../build/apk_test.gypi' ],
   #      }
 }
+
+if (enable_nacl) {
+  # Must be in a config because of how GN orders flags (otherwise -Wall will
+  # appear after this, and turn it back on).
+  config("clang_warnings") {
+    if (is_nacl_nonsfi) {
+      # There are number of platform specific functions in
+      # seccomp-bpf syscall helpers, which are not being used.
+      cflags = [ "-Wno-unused-function" ]
+    }
+  }
+
+  source_set("sandbox_linux_nacl_nonsfi") {
+    cflags = [ "-fgnu-inline-asm" ]
+    sources = [
+      # This is the subset of linux build target, needed for
+      # nacl_helper_nonsfi's sandbox implementation.
+      "bpf_dsl/bpf_dsl.cc",
+      "bpf_dsl/codegen.cc",
+      "bpf_dsl/policy.cc",
+      "bpf_dsl/policy_compiler.cc",
+      "bpf_dsl/syscall_set.cc",
+      "seccomp-bpf-helpers/sigsys_handlers.cc",
+      "seccomp-bpf-helpers/syscall_parameters_restrictions.cc",
+      "seccomp-bpf/die.cc",
+      "seccomp-bpf/sandbox_bpf.cc",
+      "seccomp-bpf/syscall.cc",
+      "seccomp-bpf/trap.cc",
+      "services/credentials.cc",
+      "services/namespace_sandbox.cc",
+      "services/namespace_utils.cc",
+      "services/proc_util.cc",
+      "services/resource_limits.cc",
+      "services/syscall_wrappers.cc",
+      "services/thread_helpers.cc",
+      "suid/client/setuid_sandbox_client.cc",
+    ]
+
+    configs += [ ":clang_warnings" ]
+  }
+}