generate_test_[keys/cert_macros]: minor fixes

- remove new line at beginning of test_keys.h
- add footer at the end of both generated files

Signed-off-by: Valerio Setti <valerio.setti@nordicsemi.no>

tests/data_files/test_certs.h.jinja2

@@ -40,3 +40,4 @@
     {% endif %}
 
 {% endfor %}
+/* End of generated file */

tests/scripts/generate_test_cert_macros.py

@@ -72,7 +72,8 @@ def generate(values=[], output=None):
     """
     template_loader = jinja2.FileSystemLoader(DATA_FILES_PATH)
     template_env = jinja2.Environment(
-        loader=template_loader, lstrip_blocks=True, trim_blocks=True)
+        loader=template_loader, lstrip_blocks=True, trim_blocks=True,
+        keep_trailing_newline=True)
 
     def read_as_c_array(filename):
         with open(filename, 'rb') as f:

tests/scripts/generate_test_keys.py

@@ -92,7 +92,7 @@ def get_look_up_table_entry(key_type: str, group_id_or_keybits: str,
 
 def write_output_file(output_file_name: str, arrays: List[str], look_up_table: List[str]):
     with open(output_file_name, 'wt') as output:
-        output.write("""
+        output.write("""\
 /*********************************************************************************
  * This file was automatically generated from tests/scripts/generate_test_keys.py.
  * Please do not edit it manually.
@@ -112,6 +112,8 @@ struct predefined_key_element {{
 struct predefined_key_element predefined_keys[] = {{
 {}
 }};
+
+/* End of generated file */
 """.format("\n".join(look_up_table)))