feat(build): make liteos_config_file available as gn argument

You can specify another config file in hb build like this:
  hb build --gn-args liteos_config_file=myconfig.config
file specified in liteos_config_file argument is relative
to "$product_path/kernel_configs" directory, or is an
absolute file path, for example:
  hb build --gn-args liteos_config_file=//path/to/myconfig.config
or
  hb build --gn-args liteos_config_file=/another/path/to/myconfig.config
Signed-off-by: NCaoruihong <crh.cao@huawei.com>
Change-Id: I7e98604006feff9c2487e06a8f3f2a11e5de746b

BUILD.gn

@@ -45,7 +45,11 @@ if (tee_enable) {
   tee = "_tee"
 }
 
-liteos_config_file = "$product_path/kernel_configs/${ohos_build_type}${tee}.config"
+declare_args() {
+  liteos_config_file = "${ohos_build_type}${tee}.config"
+}
+
+liteos_config_file = rebase_path(liteos_config_file, "", "$product_path/kernel_configs")
 print("liteos_config_file:", liteos_config_file)
 
 exec_script("//build/lite/run_shell_cmd.py",