third_party/emboss: Use action() instead of pw_python_action()

Use action() instead of pw_python_action() for the Emboss compiler
action to work around pw_python_action() not being hermetic. Hermeticity
errors are treated as errors on Fuchsia.

Change-Id: I95f1179aa985530d3516fca937dad8a691b6e0bf
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/127142
Reviewed-by: Ali Saeed <saeedali@google.com>
Commit-Queue: Ben Lawson <benlawson@google.com>
diff --git a/third_party/emboss/build_defs.gni b/third_party/emboss/build_defs.gni
index 229d1e0..74bd061 100644
--- a/third_party/emboss/build_defs.gni
+++ b/third_party/emboss/build_defs.gni
@@ -13,7 +13,6 @@
 # the License.
 
 import("//build_overrides/pigweed.gni")
-import("$dir_pw_build/python_action.gni")
 import("$dir_pw_third_party/emboss/emboss.gni")
 
 # Compiles a .emb file into a .h file.
@@ -73,7 +72,7 @@
   default_import_dir = get_path_info(default_import_dir, "dir")
   default_import_dir = rebase_path(default_import_dir, root_build_dir)
 
-  pw_python_action(target_name + "_header") {
+  action(target_name + "_header") {
     script = "$dir_pw_third_party/emboss/embossc_runner.py"
 
     args = [