I have never seen or used the "execution_dir". As such I would delete it, unless it is really required. You can comment it out for the time being (<!-- Option execution_dir="../minimal" -->).
In the C::B plugin build project files some did not have an entry for the "working_dir", but where it did exist it was set to the same directory as the "output" where I looked. I would either remove it or set it to $(TARGET_OUTPUT_DIR) so that you do not have to update two lines in the project file going forward if you change the output directory.
Some other changes could be:
1. As they are sample apps I would change the compiler options to enable debugging and no optimisation (-g -O0 -ggdb) plus remove the linker "-s" option.
2. Add a "<Option default_target="TBA" />"
3. Remove the target "<Option compiler="gcc" />" option so that there is only one at the project level
I have not done this or tried this, but you could add a <ExtraCommands> before to check that the $(#WX_CONFIG) is defined and if not the use the script expansion facility to pop up a message dialog to indicate that they have to set the global variable. See
https://wiki.codeblocks.org/index.php/Variable_expansion for the script expansion info/example.
BTW I should update my project files to change the working_dir to $(TARGET_OUTPUT_DIR). I will update my bulk CBP app to make the change in the next day or two.