GN: forward_variables_from shouldn't clobber vars.

build/config/nacl/rules.gni

 # Copyright 2015 The Native Client 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/features.gni")
 import("//build/config/nacl/config.gni")
 
 # Generate a nmf file
 #
 # Native Client Manifest (nmf) is a JSON file that tells the browser where to
 # download and load Native Client application files and libraries.
 #
 # Variables:
 #   executables: .nexe/.pexe/.bc executables to generate nmf for
 #   lib_prefix: path to prepend to shared libraries in the nmf
 #   nmf: the name and the path of the output file
 #   nmfflags: additional flags for the nmf generator
 #   stage_dependencies: directory for staging libraries
 template("generate_nmf") {
   assert(defined(invoker.executables), "Must define executables")
   assert(defined(invoker.nmf), "Must define nmf")
 
   action(target_name) {
-    nmfflags = []
-
     forward_variables_from(invoker,
                            [
                              "deps",
                              "data_deps",
                              "executables",
                              "lib_prefix",
                              "nmf",
                              "nmfflags",
                              "public_deps",
                              "stage_dependencies",
                              "testonly",
                              "visibility",
                            ])
+    if (!defined(nmfflags)) {
+      nmfflags = []
+    }
 
     # TODO(phosek): Remove this conditional once
     # https://bugs.chromium.org/p/nativeclient/issues/detail?id=4339 is
     # resolved.
     if (current_cpu == "pnacl") {
       objdump = rebase_path("${nacl_toolchain_bindir}/x86_64-nacl-objdump")
     } else {
       objdump = rebase_path("${nacl_toolprefix}objdump")
     }
     if (host_os == "win") {
@@ skipping 63 matching lines @@
 #
 # Variables:
 #   executable: Non-SFI .nexe executable to generate nmf for
 #   nmf: the name and the path of the output file
 #   nmfflags: additional flags for the nmf generator
 template("generate_nonsfi_test_nmf") {
   assert(defined(invoker.executable), "Must define executable")
   assert(defined(invoker.nmf), "Must define nmf")
 
   action(target_name) {
-    nmfflags = []
-
     forward_variables_from(invoker,
                            [
                              "deps",
                              "data_deps",
                              "executable",
                              "nmf",
-                             "nmfflags",
                              "testonly",
                              "public_deps",
                              "visibility",
                            ])
 
     script = "//ppapi/tests/create_nonsfi_test_nmf.py"
     sources = [
       executable,
     ]
     outputs = [
       nmf,
     ]
 
     # NOTE: We use target_cpu rather than current_cpu on purpose because
     # current_cpu is always going to be pnacl for Non-SFI, but the Non-SFI
     # .nexe executable is always translated to run on the target machine.
     if (target_cpu == "x86") {
       arch = "x86-32"
     } else if (target_cpu == "x64") {
       arch = "x86-64"
     } else {
       arch = target_cpu
     }
     args = [
-             "--program=" + rebase_path(executable, root_build_dir),
-             "--arch=${arch}",
-             "--output=" + rebase_path(nmf, root_build_dir),
-           ] + nmfflags
+      "--program=" + rebase_path(executable, root_build_dir),
+      "--arch=${arch}",
+      "--output=" + rebase_path(nmf, root_build_dir),
+    ]
+    if (defined(invoker.nmfflags)) {
+      args += invoker.nmfflags
+    }
   }
 }