SImplify linkerscirpt usage

Avoids assigning to things that we can't assign

Author: theotherjimmy

tools/export/embitz/__init__.py

@@ -64,17 +64,13 @@ def generate(self):
             l, _ = splitext(basename(lib))
             libraries.append(l[3:])
 
-
-        if self.resources.linker_script is None:
-            self.resources.linker_script = ''
-
         ctx = {
             'name': self.project_name,
             'target': self.target,
             'toolchain': self.toolchain.name,
             'source_files': source_files,
             'include_paths': self.resources.inc_dirs,
-            'script_file': self.resources.linker_script,
+            'script_file': self.resources.linker_script or '',
             'library_paths': self.resources.lib_dirs,
             'libraries': libraries,
             'symbols': self.toolchain.get_symbols(),