support ext args

Signed-off-by: steven_q <qichanggui@huawei.com>
Change-Id: Iaef3143b1a49b3d9de8d37d2c00c6428edb410a1

BUILD.gn

@@ -491,6 +491,11 @@ action("build_contexts") {
     "--components",
     components,
   ]
+  if (contexts_extra_args != "default") {
+    foreach(arg, string_split(contexts_extra_args, " ")) {
+      args += [ arg ]
+    }
+  }
   deps = [
     ":build_policy",
     "$THIRD_PARTY_DIR/selinux:sefcontext_compile($host_toolchain)",

selinux.gni

@@ -21,6 +21,7 @@ declare_args() {
   special_build_policy_script = "default"
   special_build_contexts_script = "default"
   extra_args = "default"
+  contexts_extra_args = "default"
 }
 
 declare_args() {