Fix temp file leak

Found using the `EMTEST_DETECT_TEMPFILE_LEAKS=1` env variable.

Author: kleisauke

emcc.py

@@ -3016,6 +3016,7 @@ def phase_final_emitting(options, state, target, wasm_target, memfile):
     src = read_file(final_js)
     final_js += '.esmeta.js'
     write_file(final_js, src.replace('EMSCRIPTEN$IMPORT$META', 'import.meta'))
+    shared.get_temp_files().note(final_js)
     save_intermediate('es6-import-meta')
 
   # Apply pre and postjs files