Allow user overrides of LINKER_SCRIPT Make variable

Author: Max Vilimpoc

tools/export/makefile/Makefile.tmpl

@@ -55,7 +55,12 @@ PROJECT := {{name}}
 {% endfor %}
 LIBRARY_PATHS :={% for p in library_paths %} {{user_library_flag}}{{p}} {% endfor %}
 LIBRARIES :={% for lib in libraries %} {{lib}} {% endfor %}
+
+# Allow user overrides of LINKER_SCRIPT from the command line, useful
+# if user wants to reserve specific flash areas for production config data
+ifndef $(LINKER_SCRIPT)
 LINKER_SCRIPT := {{linker_script}}
+endif
 {%- block additional_variables -%}{% endblock %}
 
 # Objects and Paths