Update: Disable -fstrict-flex-arrays=3 flag because it doesn't work on GCC 11.

Update: Disable -fstrict-flex-arrays=3 flag because it doesn't work on GCC 11.

I just did tests on GCC 11, which is not too old.
The -fstrict-flex-arrays flag does not work there.
For now, just disable the flag by setting it to the non-existent gcc_13 mode.
The mode can be added to the mode list and enabled if so desired.
I may make version specific modes available in the future (or not) but that will require some planning.
The fakefile should be designed to test the GCC version, but I would rather avoid such logic by design.
Let the distributor or the system administrator handle such decisions.